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imgui/backends/imgui_impl_metal4.mm

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// dear imgui: Renderer Backend for Metal 4
// This needs to be used along with a Platform Backend (e.g. OSX)
// Implemented features:
// [X] Renderer: User texture binding. Use 'MTLTexture' as texture identifier. Read the FAQ about ImTextureID/ImTextureRef!
// [X] Renderer: Large meshes support (64k+ vertices) even with 16-bit indices (ImGuiBackendFlags_RendererHasVtxOffset).
// [X] Renderer: Texture updates support for dynamic font atlas (ImGuiBackendFlags_RendererHasTextures).
// Missing features or Issues:
// [ ] Metal-cpp support.
// [ ] Texture view pool support? Reevaluate which type to use for ImtextureID.
// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
// Learn about Dear ImGui:
// - FAQ https://dearimgui.com/faq
// - Getting Started https://dearimgui.com/getting-started
// - Documentation https://dearimgui.com/docs (same as your local docs/ folder).
// - Introduction, links and more at the top of imgui.cpp
// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
// 2026-07-02: Metal 4: Added new Metal 4 backend implementation. (#9458)
#include "imgui.h"
#ifndef IMGUI_DISABLE
#include "imgui_impl_metal4.h"
#import <time.h>
#import <Metal/Metal.h>
#pragma mark - Support classes and structs
struct ImGui_Metal4_ConstantData
{
float ModelViewProjectionMatrix[4][4];
};
@interface MetalBuffer : NSObject
@property (nonatomic, strong) id<MTLBuffer> buffer;
@property (nonatomic, assign) double lastReuseTime;
- (instancetype)initWithBuffer:(id<MTLBuffer>)buffer;
@end
// An object that encapsulates the data necessary to uniquely identify a
// render pipeline state. These are used as cache keys.
@interface FramebufferDescriptor : NSObject<NSCopying>
@property (nonatomic, assign) unsigned long sampleCount;
@property (nonatomic, assign) MTLPixelFormat colorPixelFormat;
@property (nonatomic, assign) MTLPixelFormat depthPixelFormat;
@property (nonatomic, assign) MTLPixelFormat stencilPixelFormat;
- (instancetype)initWithRenderPassDescriptor:(MTL4RenderPassDescriptor*)renderPassDescriptor;
@end
@interface MetalTexture : NSObject
@property (nonatomic, strong) id<MTLTexture> metalTexture;
- (instancetype)initWithTexture:(id<MTLTexture>)metalTexture;
@end
// A singleton that stores long-lived objects that are needed by the Metal
// renderer backend. Stores the render pipeline state cache and the default
// font texture, and manages the reusable buffer cache.
@interface MetalContext : NSObject
@property (nonatomic, strong) id<MTLDevice> device;
@property (nonatomic, strong) id<MTL4CommandQueue> commandQueue;
@property (nonatomic, strong) id<MTLDepthStencilState> depthStencilState;
@property (nonatomic, strong) id<MTL4ArgumentTable> argumentTable;
@property (nonatomic, strong) id<MTLSamplerState> samplerStateLinear;
@property (nonatomic, strong) id<MTLSamplerState> samplerStateNearest;
@property (nonatomic, strong) id<MTLResidencySet> residencySet;
@property (nonatomic, strong) FramebufferDescriptor* framebufferDescriptor;
@property (nonatomic, strong) NSMutableDictionary* renderPipelineStateCache;
@property (nonatomic, assign) NSUInteger framesInFlight;
@property (nonatomic, assign) NSUInteger currentFrameSlot;
@property (nonatomic, strong) NSArray<id<MTLBuffer>>* constantBuffers;
@property (nonatomic, assign) ImGui_Metal4_ConstantData** constantBufferContentsArray;
@property (nonatomic, strong) NSMutableArray<NSMutableArray<MetalBuffer*>*>* bufferCaches;
@property (nonatomic, strong) NSObject* bufferCacheLock;
@property (nonatomic, assign) double lastBufferCachePurge;
- (id<MTLBuffer>)currentConstantBuffer;
- (ImGui_Metal4_ConstantData*)currentConstantBufferContents;
- (MetalBuffer*)dequeueReusableBufferOfLength:(NSUInteger)length device:(id<MTLDevice>)device;
- (id<MTLRenderPipelineState>)renderPipelineStateForFramebufferDescriptor:(FramebufferDescriptor*)descriptor device:(id<MTLDevice>)device;
@end
struct ImGui_ImplMetal4_Data
{
MetalContext* SharedMetalContext;
id<MTL4RenderCommandEncoder> RenderCommandEncoder;
ImGui_ImplMetal4_Data() { memset((void*)this, 0, sizeof(*this)); }
};
static ImGui_ImplMetal4_Data* ImGui_ImplMetal4_GetBackendData() { return ImGui::GetCurrentContext() ? (ImGui_ImplMetal4_Data*)ImGui::GetIO().BackendRendererUserData : nullptr; }
static void ImGui_ImplMetal4_DestroyBackendData(){ IM_DELETE(ImGui_ImplMetal4_GetBackendData()); }
static inline CFTimeInterval GetMachAbsoluteTimeInSeconds() { return (CFTimeInterval)(double)(clock_gettime_nsec_np(CLOCK_UPTIME_RAW) / 1e9); }
#pragma mark - Dear ImGui Metal Backend API
void ImGui_ImplMetal4_NewFrame(MTL4RenderPassDescriptor* renderPassDescriptor, int frameInFlightIndex)
{
ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData();
IM_ASSERT(bd != nil && "Context or backend not initialized! Did you call ImGui_ImplMetal4_Init()?");
IM_ASSERT(frameInFlightIndex < bd->SharedMetalContext.framesInFlight && "frameInFlightIndex out of range! See framesInFlight passed to ImGui_ImplMetal4_Init().");
#ifdef IMGUI_IMPL_METAL_CPP
bd->SharedMetalContext.framebufferDescriptor = [[[FramebufferDescriptor alloc] initWithRenderPassDescriptor:renderPassDescriptor]autorelease];
#else
bd->SharedMetalContext.framebufferDescriptor = [[FramebufferDescriptor alloc] initWithRenderPassDescriptor:renderPassDescriptor];
#endif
bd->SharedMetalContext.currentFrameSlot = (NSUInteger)frameInFlightIndex;
if (bd->SharedMetalContext.depthStencilState == nil)
ImGui_ImplMetal4_CreateDeviceObjects(bd->SharedMetalContext.device);
}
static void ImGui_ImplMetal4_SetupRenderState(ImDrawData* draw_data, id<MTL4CommandBuffer> commandBuffer,
id<MTL4RenderCommandEncoder> commandEncoder, id<MTLRenderPipelineState> renderPipelineState,
MetalBuffer* vertexBuffer, size_t vertexBufferOffset)
{
IM_UNUSED(commandBuffer);
ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData();
[commandEncoder setCullMode:MTLCullModeNone];
[commandEncoder setDepthStencilState:bd->SharedMetalContext.depthStencilState];
// Setup viewport, orthographic projection matrix
// Our visible imgui space lies from draw_data->DisplayPos (top left) to
// draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayMin is typically (0,0) for single viewport apps.
MTLViewport viewport =
{
.originX = 0.0,
.originY = 0.0,
.width = (double)(draw_data->DisplaySize.x * draw_data->FramebufferScale.x),
.height = (double)(draw_data->DisplaySize.y * draw_data->FramebufferScale.y),
.znear = 0.0,
.zfar = 1.0
};
[commandEncoder setViewport:viewport];
float L = draw_data->DisplayPos.x;
float R = draw_data->DisplayPos.x + draw_data->DisplaySize.x;
float T = draw_data->DisplayPos.y;
float B = draw_data->DisplayPos.y + draw_data->DisplaySize.y;
float N = (float)viewport.znear;
float F = (float)viewport.zfar;
const float ortho_projection[4][4] =
{
{ 2.0f/(R-L), 0.0f, 0.0f, 0.0f },
{ 0.0f, 2.0f/(T-B), 0.0f, 0.0f },
{ 0.0f, 0.0f, 1/(F-N), 0.0f },
{ (R+L)/(L-R), (T+B)/(B-T), N/(F-N), 1.0f },
};
ImGui_Metal4_ConstantData* constantBufferContents = [bd->SharedMetalContext currentConstantBufferContents];
memcpy(constantBufferContents->ModelViewProjectionMatrix, ortho_projection, sizeof(ortho_projection));
id<MTL4ArgumentTable> argumentTable = bd->SharedMetalContext.argumentTable;
[argumentTable setAddress:[bd->SharedMetalContext currentConstantBuffer].gpuAddress atIndex:1];
[argumentTable setAddress:(vertexBuffer.buffer.gpuAddress + vertexBufferOffset) attributeStride:sizeof(ImDrawVert) atIndex:0];
[argumentTable setSamplerState:bd->SharedMetalContext.samplerStateLinear.gpuResourceID atIndex:0];
[commandEncoder setArgumentTable:argumentTable atStages:MTLRenderStageVertex | MTLRenderStageFragment];
[commandEncoder setRenderPipelineState:renderPipelineState];
}
static void ImGui_ImplMetal4_DrawCallback_ResetRenderState(const ImDrawList*, const ImDrawCmd*) {} // Intentionally empty. Used as an identifier for rendering loop to call its code. Simpler to implement this way.
static void ImGui_ImplMetal4_DrawCallback_SetSamplerLinear(const ImDrawList*, const ImDrawCmd*) { ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData(); [bd->SharedMetalContext.argumentTable setSamplerState:bd->SharedMetalContext.samplerStateLinear.gpuResourceID atIndex:0]; }
static void ImGui_ImplMetal4_DrawCallback_SetSamplerNearest(const ImDrawList*, const ImDrawCmd*) { ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData(); [bd->SharedMetalContext.argumentTable setSamplerState:bd->SharedMetalContext.samplerStateNearest.gpuResourceID atIndex:0]; }
void ImGui_ImplMetal4_RenderDrawData(ImDrawData* draw_data, id<MTL4CommandBuffer> commandBuffer, id<MTL4RenderCommandEncoder> commandEncoder)
{
ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData();
MetalContext* ctx = bd->SharedMetalContext;
// Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
int fb_width = (int)(draw_data->DisplaySize.x * draw_data->FramebufferScale.x);
int fb_height = (int)(draw_data->DisplaySize.y * draw_data->FramebufferScale.y);
if (fb_width <= 0 || fb_height <= 0 || draw_data->CmdLists.Size == 0)
return;
// Catch up with texture updates. Most of the times, the list will have 1 element with an OK status, aka nothing to do.
// (This almost always points to ImGui::GetPlatformIO().Textures[] but is part of ImDrawData to allow overriding or disabling texture updates).
if (draw_data->Textures != nullptr)
for (ImTextureData* tex : *draw_data->Textures)
if (tex->Status != ImTextureStatus_OK)
ImGui_ImplMetal4_UpdateTexture(tex);
// Try to retrieve a render pipeline state that is compatible with the framebuffer config for this frame
// The hit rate for this cache should be very near 100%.
id<MTLRenderPipelineState> renderPipelineState = ctx.renderPipelineStateCache[ctx.framebufferDescriptor];
if (renderPipelineState == nil)
{
// No luck; make a new render pipeline state
renderPipelineState = [ctx renderPipelineStateForFramebufferDescriptor:ctx.framebufferDescriptor device:commandBuffer.device];
// Cache render pipeline state for later reuse
ctx.renderPipelineStateCache[ctx.framebufferDescriptor] = renderPipelineState;
}
size_t vertexBufferLength = (size_t)draw_data->TotalVtxCount * sizeof(ImDrawVert);
size_t indexBufferLength = (size_t)draw_data->TotalIdxCount * sizeof(ImDrawIdx);
MetalBuffer* vertexBuffer = [ctx dequeueReusableBufferOfLength:vertexBufferLength device:commandBuffer.device];
MetalBuffer* indexBuffer = [ctx dequeueReusableBufferOfLength:indexBufferLength device:commandBuffer.device];
bd->RenderCommandEncoder = commandEncoder;
ImGui_ImplMetal4_SetupRenderState(draw_data, commandBuffer, commandEncoder, renderPipelineState, vertexBuffer, 0);
// Will project scissor/clipping rectangles into framebuffer space
ImVec2 clip_off = draw_data->DisplayPos; // (0,0) unless using multi-viewports
ImVec2 clip_scale = draw_data->FramebufferScale; // (1,1) unless using retina display which are often (2,2)
// Before rendering command lists, commit residency set
[bd->SharedMetalContext.residencySet commit];
// Render command lists
size_t vertexBufferOffset = 0;
size_t indexBufferOffset = 0;
for (const ImDrawList* draw_list : draw_data->CmdLists)
{
memcpy((char*)vertexBuffer.buffer.contents + vertexBufferOffset, draw_list->VtxBuffer.Data, (size_t)draw_list->VtxBuffer.Size * sizeof(ImDrawVert));
memcpy((char*)indexBuffer.buffer.contents + indexBufferOffset, draw_list->IdxBuffer.Data, (size_t)draw_list->IdxBuffer.Size * sizeof(ImDrawIdx));
for (int cmd_i = 0; cmd_i < draw_list->CmdBuffer.Size; cmd_i++)
{
const ImDrawCmd* pcmd = &draw_list->CmdBuffer[cmd_i];
if (pcmd->UserCallback)
{
// User callback, registered via ImDrawList::AddCallback()
if (pcmd->UserCallback == ImGui_ImplMetal4_DrawCallback_ResetRenderState)
ImGui_ImplMetal4_SetupRenderState(draw_data, commandBuffer, commandEncoder, renderPipelineState, vertexBuffer, vertexBufferOffset);
else
pcmd->UserCallback(draw_list, pcmd);
}
else
{
// Project scissor/clipping rectangles into framebuffer space
ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);
ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y);
// Clamp to viewport as setScissorRect() won't accept values that are off bounds
if (clip_min.x < 0.0f) { clip_min.x = 0.0f; }
if (clip_min.y < 0.0f) { clip_min.y = 0.0f; }
if (clip_max.x > (float)fb_width) { clip_max.x = (float)fb_width; }
if (clip_max.y > (float)fb_height) { clip_max.y = (float)fb_height; }
if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)
continue;
if (pcmd->ElemCount == 0) // drawIndexedPrimitives() validation doesn't accept this
continue;
// Apply scissor/clipping rectangle
MTLScissorRect scissorRect =
{
.x = NSUInteger(clip_min.x),
.y = NSUInteger(clip_min.y),
.width = NSUInteger(clip_max.x - clip_min.x),
.height = NSUInteger(clip_max.y - clip_min.y)
};
[commandEncoder setScissorRect:scissorRect];
// Bind texture, Draw
ImTextureID tex_id = pcmd->GetTexID();
if (tex_id != ImTextureID_Invalid)
{
id<MTLTexture> texture = (__bridge id<MTLTexture>)(void*)(intptr_t)tex_id;
[bd->SharedMetalContext.argumentTable setTexture:texture.gpuResourceID atIndex:0];
}
[bd->SharedMetalContext.argumentTable setAddress:(vertexBuffer.buffer.gpuAddress + vertexBufferOffset + (pcmd->VtxOffset * sizeof(ImDrawVert))) attributeStride:sizeof(ImDrawVert) atIndex:0];
size_t indexBufferCmdOffset = indexBufferOffset + (pcmd->IdxOffset * sizeof(ImDrawIdx));
[commandEncoder drawIndexedPrimitives:MTLPrimitiveTypeTriangle
indexCount:pcmd->ElemCount
indexType:sizeof(ImDrawIdx) == 2 ? MTLIndexTypeUInt16 : MTLIndexTypeUInt32
indexBuffer:indexBuffer.buffer.gpuAddress + indexBufferCmdOffset
indexBufferLength:indexBuffer.buffer.length - indexBufferCmdOffset];
}
}
vertexBufferOffset += (size_t)draw_list->VtxBuffer.Size * sizeof(ImDrawVert);
indexBufferOffset += (size_t)draw_list->IdxBuffer.Size * sizeof(ImDrawIdx);
}
MetalContext* sharedMetalContext = bd->SharedMetalContext;
@synchronized(sharedMetalContext.bufferCacheLock)
{
NSMutableArray<MetalBuffer*>* slotCache = sharedMetalContext.bufferCaches[sharedMetalContext.currentFrameSlot];
[slotCache addObject:vertexBuffer];
[slotCache addObject:indexBuffer];
}
bd->RenderCommandEncoder = nil;
}
static void ImGui_ImplMetal4_DestroyTexture(ImTextureData* tex)
{
if (MetalTexture* backend_tex = (__bridge_transfer MetalTexture*)(tex->BackendUserData))
{
IM_ASSERT(backend_tex.metalTexture == (__bridge id<MTLTexture>)(void*)(intptr_t)tex->TexID);
backend_tex.metalTexture = nil;
// Clear identifiers and mark as destroyed (in order to allow e.g. calling InvalidateDeviceObjects while running)
tex->SetTexID(ImTextureID_Invalid);
tex->BackendUserData = nullptr;
}
tex->SetStatus(ImTextureStatus_Destroyed);
}
void ImGui_ImplMetal4_UpdateTexture(ImTextureData* tex)
{
ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData();
if (tex->Status == ImTextureStatus_WantCreate)
{
// Create and upload new texture to graphics system
//IMGUI_DEBUG_LOG("UpdateTexture #%03d: WantCreate %dx%d\n", tex->UniqueID, tex->Width, tex->Height);
IM_ASSERT(tex->TexID == ImTextureID_Invalid && tex->BackendUserData == nullptr);
IM_ASSERT(tex->Format == ImTextureFormat_RGBA32);
// We are retrieving and uploading the font atlas as a 4-channels RGBA texture here.
// In theory we could call GetTexDataAsAlpha8() and upload a 1-channel texture to save on memory access bandwidth.
// However, using a shader designed for 1-channel texture would make it less obvious to use the ImTextureID facility to render users own textures.
// You can make that change in your implementation.
MTLTextureDescriptor* textureDescriptor = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:MTLPixelFormatRGBA8Unorm
width:(NSUInteger)tex->Width
height:(NSUInteger)tex->Height
mipmapped:NO];
textureDescriptor.usage = MTLTextureUsageShaderRead;
textureDescriptor.storageMode = MTLStorageModeShared;
id <MTLTexture> texture = [bd->SharedMetalContext.device newTextureWithDescriptor:textureDescriptor];
[bd->SharedMetalContext.residencySet addAllocation:texture];
[texture replaceRegion:MTLRegionMake2D(0, 0, (NSUInteger)tex->Width, (NSUInteger)tex->Height) mipmapLevel:0 withBytes:tex->Pixels bytesPerRow:(NSUInteger)tex->Width * 4];
MetalTexture* backend_tex = [[MetalTexture alloc] initWithTexture:texture];
// Store identifiers
tex->SetTexID((ImTextureID)(intptr_t)texture);
tex->SetStatus(ImTextureStatus_OK);
tex->BackendUserData = (__bridge_retained void*)(backend_tex);
}
else if (tex->Status == ImTextureStatus_WantUpdates)
{
// Update selected blocks. We only ever write to textures regions which have never been used before!
// This backend choose to use tex->Updates[] but you can use tex->UpdateRect to upload a single region.
MetalTexture* backend_tex = (__bridge MetalTexture*)(tex->BackendUserData);
for (ImTextureRect& r : tex->Updates)
{
[backend_tex.metalTexture replaceRegion:MTLRegionMake2D((NSUInteger)r.x, (NSUInteger)r.y, (NSUInteger)r.w, (NSUInteger)r.h)
mipmapLevel:0
withBytes:tex->GetPixelsAt(r.x, r.y)
bytesPerRow:(NSUInteger)tex->Width * 4];
}
tex->SetStatus(ImTextureStatus_OK);
}
else if (tex->Status == ImTextureStatus_WantDestroy && tex->UnusedFrames > 0)
{
ImGui_ImplMetal4_DestroyTexture(tex);
}
}
bool ImGui_ImplMetal4_CreateDeviceObjects(id<MTLDevice> device)
{
ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData();
MTLResidencySetDescriptor* residencySetDescriptor = [[MTLResidencySetDescriptor alloc] init];
residencySetDescriptor.initialCapacity = 1000;
NSError* error = nil;
bd->SharedMetalContext.residencySet = [device newResidencySetWithDescriptor:residencySetDescriptor error:&error];
IM_ASSERT(bd->SharedMetalContext.residencySet != nil && error == nil);
[bd->SharedMetalContext.commandQueue addResidencySet:bd->SharedMetalContext.residencySet];
MTLDepthStencilDescriptor* depthStencilDescriptor = [[MTLDepthStencilDescriptor alloc] init];
depthStencilDescriptor.depthWriteEnabled = NO;
depthStencilDescriptor.depthCompareFunction = MTLCompareFunctionAlways;
bd->SharedMetalContext.depthStencilState = [device newDepthStencilStateWithDescriptor:depthStencilDescriptor];
MTLSamplerDescriptor* samplerDescriptor = [[MTLSamplerDescriptor alloc] init];
samplerDescriptor.supportArgumentBuffers = YES;
samplerDescriptor.minFilter = MTLSamplerMinMagFilterLinear;
samplerDescriptor.magFilter = MTLSamplerMinMagFilterLinear;
samplerDescriptor.mipFilter = MTLSamplerMipFilterLinear;
bd->SharedMetalContext.samplerStateLinear = [device newSamplerStateWithDescriptor:samplerDescriptor];
samplerDescriptor.minFilter = MTLSamplerMinMagFilterNearest;
samplerDescriptor.magFilter = MTLSamplerMinMagFilterNearest;
samplerDescriptor.mipFilter = MTLSamplerMipFilterNearest;
bd->SharedMetalContext.samplerStateNearest = [device newSamplerStateWithDescriptor:samplerDescriptor];
NSMutableArray<id<MTLBuffer>>* constantBuffers = [NSMutableArray array];
ImGui_Metal4_ConstantData** constantBufferContentsArray = (ImGui_Metal4_ConstantData**)malloc(sizeof(ImGui_Metal4_ConstantData*) * bd->SharedMetalContext.framesInFlight);
for (NSUInteger i = 0; i < bd->SharedMetalContext.framesInFlight; i++)
{
id<MTLBuffer> constantBuffer = [device newBufferWithLength:sizeof(ImGui_Metal4_ConstantData) options:MTLResourceStorageModeShared];
[constantBuffers addObject:constantBuffer];
constantBufferContentsArray[i] = (ImGui_Metal4_ConstantData*)constantBuffer.contents;
[bd->SharedMetalContext.residencySet addAllocation:constantBuffer];
}
bd->SharedMetalContext.constantBuffers = constantBuffers;
bd->SharedMetalContext.constantBufferContentsArray = constantBufferContentsArray;
MTL4ArgumentTableDescriptor* argumentTableDescriptor = [[MTL4ArgumentTableDescriptor alloc] init];
argumentTableDescriptor.maxBufferBindCount = 8;
argumentTableDescriptor.maxTextureBindCount = 8;
argumentTableDescriptor.maxSamplerStateBindCount = 8;
argumentTableDescriptor.supportAttributeStrides = YES; // required: vertex buffer is bound via setAddress:stride:atIndex: for stage_in fetch
bd->SharedMetalContext.argumentTable = [device newArgumentTableWithDescriptor:argumentTableDescriptor error:&error];
IM_ASSERT(bd->SharedMetalContext.argumentTable != nil && error == nil);
return true;
}
void ImGui_ImplMetal4_DestroyDeviceObjects()
{
ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData();
// Destroy all textures
for (ImTextureData* tex : ImGui::GetPlatformIO().Textures)
if (tex->RefCount == 1)
ImGui_ImplMetal4_DestroyTexture(tex);
[bd->SharedMetalContext.renderPipelineStateCache removeAllObjects];
bd->SharedMetalContext.samplerStateLinear = nil;
bd->SharedMetalContext.samplerStateNearest = nil;
}
bool ImGui_ImplMetal4_Init(id<MTLDevice> device, id<MTL4CommandQueue> commandQueue, int framesInFlight)
{
ImGuiIO& io = ImGui::GetIO();
IMGUI_CHECKVERSION();
IM_ASSERT(io.BackendRendererUserData == nullptr && "Already initialized a renderer backend!");
IM_ASSERT(framesInFlight > 0 && "framesInFlight must be at least 1!");
ImGui_ImplMetal4_Data* bd = IM_NEW(ImGui_ImplMetal4_Data)();
io.BackendRendererUserData = (void*)bd;
io.BackendRendererName = "imgui_impl_metal4";
io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset; // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
io.BackendFlags |= ImGuiBackendFlags_RendererHasTextures; // We can honor ImGuiPlatformIO::Textures[] requests during render.
ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
platform_io.DrawCallback_ResetRenderState = ImGui_ImplMetal4_DrawCallback_ResetRenderState;
platform_io.DrawCallback_SetSamplerLinear = ImGui_ImplMetal4_DrawCallback_SetSamplerLinear;
platform_io.DrawCallback_SetSamplerNearest = ImGui_ImplMetal4_DrawCallback_SetSamplerNearest;
bd->SharedMetalContext = [[MetalContext alloc] init];
bd->SharedMetalContext.device = device;
bd->SharedMetalContext.commandQueue = commandQueue;
bd->SharedMetalContext.framesInFlight = (NSUInteger)framesInFlight;
NSMutableArray<NSMutableArray<MetalBuffer*>*>* bufferCaches = [NSMutableArray array];
for (NSUInteger i = 0; i < framesInFlight; i++)
[bufferCaches addObject:[NSMutableArray array]];
bd->SharedMetalContext.bufferCaches = bufferCaches;
return true;
}
void ImGui_ImplMetal4_Shutdown()
{
ImGui_ImplMetal4_Data* bd = ImGui_ImplMetal4_GetBackendData();
IM_UNUSED(bd);
IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");
ImGuiIO& io = ImGui::GetIO();
ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
ImGui_ImplMetal4_DestroyDeviceObjects();
ImGui_ImplMetal4_DestroyBackendData();
io.BackendRendererName = nullptr;
io.BackendRendererUserData = nullptr;
io.BackendFlags &= ~(ImGuiBackendFlags_RendererHasVtxOffset | ImGuiBackendFlags_RendererHasTextures);
platform_io.ClearRendererHandlers();
}
@implementation MetalBuffer
- (instancetype)initWithBuffer:(id<MTLBuffer>)buffer
{
if ((self = [super init]))
{
_buffer = buffer;
_lastReuseTime = GetMachAbsoluteTimeInSeconds();
}
return self;
}
@end
#pragma mark - FramebufferDescriptor implementation
@implementation FramebufferDescriptor
- (instancetype)initWithRenderPassDescriptor:(MTL4RenderPassDescriptor*)renderPassDescriptor
{
if ((self = [super init]))
{
_sampleCount = renderPassDescriptor.colorAttachments[0].texture.sampleCount;
_colorPixelFormat = renderPassDescriptor.colorAttachments[0].texture.pixelFormat;
_depthPixelFormat = renderPassDescriptor.depthAttachment.texture.pixelFormat;
_stencilPixelFormat = renderPassDescriptor.stencilAttachment.texture.pixelFormat;
}
return self;
}
- (nonnull id)copyWithZone:(nullable NSZone*)zone
{
FramebufferDescriptor* copy = [[FramebufferDescriptor allocWithZone:zone] init];
copy.sampleCount = self.sampleCount;
copy.colorPixelFormat = self.colorPixelFormat;
copy.depthPixelFormat = self.depthPixelFormat;
copy.stencilPixelFormat = self.stencilPixelFormat;
return copy;
}
- (NSUInteger)hash
{
NSUInteger sc = _sampleCount & 0x3;
NSUInteger cf = _colorPixelFormat & 0x3FF;
NSUInteger df = _depthPixelFormat & 0x3FF;
NSUInteger sf = _stencilPixelFormat & 0x3FF;
NSUInteger hash = (sf << 22) | (df << 12) | (cf << 2) | sc;
return hash;
}
- (BOOL)isEqual:(id)object
{
FramebufferDescriptor* other = object;
if (![other isKindOfClass:[FramebufferDescriptor class]])
return NO;
return other.sampleCount == self.sampleCount &&
other.colorPixelFormat == self.colorPixelFormat &&
other.depthPixelFormat == self.depthPixelFormat &&
other.stencilPixelFormat == self.stencilPixelFormat;
}
@end
#pragma mark - MetalTexture implementation
@implementation MetalTexture
- (instancetype)initWithTexture:(id<MTLTexture>)metalTexture
{
if ((self = [super init]))
self.metalTexture = metalTexture;
return self;
}
@end
#pragma mark - MetalContext implementation
@implementation MetalContext
- (instancetype)init
{
if ((self = [super init]))
{
self.renderPipelineStateCache = [NSMutableDictionary dictionary];
self.bufferCacheLock = [[NSObject alloc] init];
_lastBufferCachePurge = GetMachAbsoluteTimeInSeconds();
}
return self;
}
- (void)dealloc
{
free(_constantBufferContentsArray);
}
- (id<MTLBuffer>)currentConstantBuffer
{
return self.constantBuffers[self.currentFrameSlot];
}
- (ImGui_Metal4_ConstantData*)currentConstantBufferContents
{
return self.constantBufferContentsArray[self.currentFrameSlot];
}
- (MetalBuffer*)dequeueReusableBufferOfLength:(NSUInteger)length device:(id<MTLDevice>)device
{
double now = GetMachAbsoluteTimeInSeconds();
NSMutableArray<MetalBuffer*>* slotCache = self.bufferCaches[self.currentFrameSlot];
@synchronized(self.bufferCacheLock)
{
// Purge old buffers that haven't been useful for a while
if (now - self.lastBufferCachePurge > 1.0)
{
for (NSMutableArray<MetalBuffer*>* cache in self.bufferCaches)
{
NSMutableArray* survivors = [NSMutableArray array];
for (MetalBuffer* candidate in cache)
if (candidate.lastReuseTime > self.lastBufferCachePurge)
[survivors addObject:candidate];
[cache setArray:survivors];
}
self.lastBufferCachePurge = now;
}
// See if we have a buffer we can reuse, from this frame-in-flight slot's own cache
MetalBuffer* bestCandidate = nil;
for (MetalBuffer* candidate in slotCache)
if (candidate.buffer.length >= length && (bestCandidate == nil || bestCandidate.lastReuseTime > candidate.lastReuseTime))
bestCandidate = candidate;
if (bestCandidate != nil)
{
[slotCache removeObject:bestCandidate];
bestCandidate.lastReuseTime = now;
return bestCandidate;
}
}
// No luck; make a new buffer
id<MTLBuffer> backing = [device newBufferWithLength:length options:MTLResourceStorageModeShared];
[self.residencySet addAllocation:backing];
return [[MetalBuffer alloc] initWithBuffer:backing];
}
const char* shaderCode = R"(
#include <metal_stdlib>
using namespace metal;
struct Uniforms {
float4x4 projectionMatrix;
};
struct VertexIn {
float2 position [[attribute(0)]];
float2 texCoords [[attribute(1)]];
uchar4 color [[attribute(2)]];
};
struct VertexOut {
float4 position [[position]];
float2 texCoords;
float4 color;
};
vertex VertexOut vertex_main(VertexIn in [[stage_in]],
constant Uniforms &uniforms [[buffer(1)]])
{
VertexOut out;
out.position = uniforms.projectionMatrix * float4(in.position, 0, 1);
out.texCoords = in.texCoords;
out.color = float4(in.color) / float4(255.0);
return out;
}
fragment half4 fragment_main(VertexOut in [[stage_in]],
texture2d<half, access::sample> texture [[texture(0)]],
sampler textureSampler [[sampler(0)]])
{
half4 texColor = texture.sample(textureSampler, in.texCoords);
return half4(in.color) * texColor;
}
)";
- (id<MTLRenderPipelineState>)renderPipelineStateForFramebufferDescriptor:(FramebufferDescriptor*)descriptor device:(id<MTLDevice>)device
{
NSError* error = nil;
id<MTLLibrary> library = [device newLibraryWithSource:[NSString stringWithUTF8String:shaderCode] options:nil error:&error];
if (library == nil)
{
NSLog(@"Error: failed to create Metal library: %@", error);
return nil;
}
id<MTLFunction> vertexFunction = [library newFunctionWithName:@"vertex_main"];
id<MTLFunction> fragmentFunction = [library newFunctionWithName:@"fragment_main"];
if (vertexFunction == nil || fragmentFunction == nil)
{
NSLog(@"Error: failed to find Metal shader functions in library: %@", error);
return nil;
}
MTLVertexDescriptor* vertexDescriptor = [MTLVertexDescriptor vertexDescriptor];
vertexDescriptor.attributes[0].offset = offsetof(ImDrawVert, pos);
vertexDescriptor.attributes[0].format = MTLVertexFormatFloat2; // position
vertexDescriptor.attributes[0].bufferIndex = 0;
vertexDescriptor.attributes[1].offset = offsetof(ImDrawVert, uv);
vertexDescriptor.attributes[1].format = MTLVertexFormatFloat2; // texCoords
vertexDescriptor.attributes[1].bufferIndex = 0;
vertexDescriptor.attributes[2].offset = offsetof(ImDrawVert, col);
vertexDescriptor.attributes[2].format = MTLVertexFormatUChar4; // color
vertexDescriptor.attributes[2].bufferIndex = 0;
vertexDescriptor.layouts[0].stepRate = 1;
vertexDescriptor.layouts[0].stepFunction = MTLVertexStepFunctionPerVertex;
vertexDescriptor.layouts[0].stride = sizeof(ImDrawVert);
MTLRenderPipelineDescriptor* pipelineDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
pipelineDescriptor.vertexFunction = vertexFunction;
pipelineDescriptor.fragmentFunction = fragmentFunction;
pipelineDescriptor.vertexDescriptor = vertexDescriptor;
pipelineDescriptor.rasterSampleCount = self.framebufferDescriptor.sampleCount;
pipelineDescriptor.colorAttachments[0].pixelFormat = self.framebufferDescriptor.colorPixelFormat;
pipelineDescriptor.colorAttachments[0].blendingEnabled = YES;
pipelineDescriptor.colorAttachments[0].rgbBlendOperation = MTLBlendOperationAdd;
pipelineDescriptor.colorAttachments[0].sourceRGBBlendFactor = MTLBlendFactorSourceAlpha;
pipelineDescriptor.colorAttachments[0].destinationRGBBlendFactor = MTLBlendFactorOneMinusSourceAlpha;
pipelineDescriptor.colorAttachments[0].alphaBlendOperation = MTLBlendOperationAdd;
pipelineDescriptor.colorAttachments[0].sourceAlphaBlendFactor = MTLBlendFactorOne;
pipelineDescriptor.colorAttachments[0].destinationAlphaBlendFactor = MTLBlendFactorOneMinusSourceAlpha;
pipelineDescriptor.depthAttachmentPixelFormat = self.framebufferDescriptor.depthPixelFormat;
pipelineDescriptor.stencilAttachmentPixelFormat = self.framebufferDescriptor.stencilPixelFormat;
id<MTLRenderPipelineState> renderPipelineState = [device newRenderPipelineStateWithDescriptor:pipelineDescriptor error:&error];
if (error != nil)
NSLog(@"Error: failed to create Metal pipeline state: %@", error);
return renderPipelineState;
}
@end
//-----------------------------------------------------------------------------
#endif // #ifndef IMGUI_DISABLE