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Fonts: comments on ImTextureData fields.

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ocornut
2025-04-27 15:33:44 +02:00
committed by ocornut
parent 42e7bb80b6
commit 8140a9d8a6
2 changed files with 57 additions and 38 deletions
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59
imgui.cpp
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@@ -298,7 +298,7 @@ CODE
// Any application code here
ImGui::Text("Hello, world!");
// Render dear imgui into screen
// Render dear imgui into framebuffer
ImGui::Render();
ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
g_pSwapChain->Present(1, 0);
@@ -311,24 +311,14 @@ CODE
EXHIBIT 2: IMPLEMENTING CUSTOM BACKEND / CUSTOM ENGINE
// Application init: create a dear imgui context, setup some options, load fonts
// Application init: create a Dear ImGui context, setup some options, load fonts
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
// TODO: Set optional io.ConfigFlags values, e.g. 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard' to enable keyboard controls.
// TODO: Fill optional fields of the io structure later.
// TODO: set io.ConfigXXX values, e.g.
io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard; // Enable keyboard controls
// TODO: Load TTF/OTF fonts if you don't want to use the default font.
// Build and load the texture atlas into a texture
// (In the examples/ app this is usually done within the ImGui_ImplXXX_Init() function from one of the demo Renderer)
int width, height;
unsigned char* pixels = nullptr;
io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
// At this point you've got the texture data and you need to upload that to your graphic system:
// After we have created the texture, store its pointer/identifier (_in whichever format your engine uses_) in 'io.Fonts->TexID'.
// This will be passed back to your via the renderer. Basically ImTextureID == void*. Read FAQ for details about ImTextureID.
MyTexture* texture = MyEngine::CreateTextureFromMemoryPixels(pixels, width, height, TEXTURE_TYPE_RGBA32)
io.Fonts->SetTexID((void*)texture);
io.Fonts->AddFontFromFileTTF("NotoSans.ttf", 18.0f);
// Application main loop
while (true)
@@ -351,12 +341,19 @@ CODE
MyGameUpdate(); // may use any Dear ImGui functions, e.g. ImGui::Begin("My window"); ImGui::Text("Hello, world!"); ImGui::End();
MyGameRender(); // may use any Dear ImGui functions as well!
// Render dear imgui, swap buffers
// End the dear imgui frame
// (You want to try calling EndFrame/Render as late as you can, to be able to use Dear ImGui in your own game rendering code)
ImGui::EndFrame();
ImGui::EndFrame(); // this is automatically called by Render(), but available
ImGui::Render();
// Update textures
for (ImTextureData* tex : ImGui::GetPlatformIO().Textures)
if (tex->Status != ImTextureStatus_OK)
MyImGuiBackend_UpdateTexture(tex);
// Render dear imgui contents, swap buffers
ImDrawData* draw_data = ImGui::GetDrawData();
MyImGuiRenderFunction(draw_data);
MyImGuiBackend_RenderDrawData(draw_data);
SwapBuffers();
}
@@ -367,12 +364,32 @@ CODE
you should read the 'io.WantCaptureMouse', 'io.WantCaptureKeyboard' and 'io.WantTextInput' flags!
Please read the FAQ entry "How can I tell whether to dispatch mouse/keyboard to Dear ImGui or my application?" about this.
HOW A SIMPLE RENDERING FUNCTION MAY LOOK LIKE
---------------------------------------------
The backends in impl_impl_XXX.cpp files contain many working implementations of a rendering function.
void MyImGuiRenderFunction(ImDrawData* draw_data)
void MyImGuiBackend_UpdateTexture(ImTextureData* tex)
{
if (tex->Status == ImTextureStatus_WantCreate)
{
// create texture based on tex->Width/Height/Pixels
// call tex->SetTexID() to specify backend-specific identifiers
// tex->Status = ImTextureStatus_OK;
}
if (tex->Status == ImTextureStatus_WantUpdates)
{
// update texture blocks based on tex->UpdateRect
// tex->Status = ImTextureStatus_OK;
}
if (tex->Status == ImTextureStatus_WantDestroy)
{
// destroy texture
// call tex->SetTexID(ImTextureID_Invalid)
// tex->Status = ImTextureStatus_Destroyed;
}
}
void MyImGuiBackend_RenderDrawData(ImDrawData* draw_data)
{
// TODO: Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
// TODO: Setup texture sampling state: sample with bilinear filtering (NOT point/nearest filtering). Use 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines;' to allow point/nearest filtering.

36
imgui.h
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@@ -3079,7 +3079,7 @@ typedef void (*ImDrawCallback)(const ImDrawList* parent_list, const ImDrawCmd* c
struct ImDrawCmd
{
ImVec4 ClipRect; // 4*4 // Clipping rectangle (x1, y1, x2, y2). Subtract ImDrawData->DisplayPos to get clipping rectangle in "viewport" coordinates
ImTextureRef TexRef; // 16 // User-provided texture ID. Set by user in ImFontAtlas::SetTexID() for fonts or passed to Image*() functions. Ignore if never using images or multiple fonts atlas.
ImTextureRef TexRef; // 16 // Reference to a font/texture atlas (where backend called ImTextureData::SetTexID()) or to a user-provided texture ID (via e.g. ImGui::Image() calls). Both will lead to a ImTextureID value.
unsigned int VtxOffset; // 4 // Start offset in vertex buffer. ImGuiBackendFlags_RendererHasVtxOffset: always 0, otherwise may be >0 to support meshes larger than 64K vertices with 16-bit indices.
unsigned int IdxOffset; // 4 // Start offset in index buffer.
unsigned int ElemCount; // 4 // Number of indices (multiple of 3) to be rendered as triangles. Vertices are stored in the callee ImDrawList's vtx_buffer[] array, indices in idx_buffer[].
@@ -3403,24 +3403,26 @@ struct ImTextureRect
// Why does we store two identifiers: TexID and BackendUserData?
// - ImTextureID TexID = lower-level identifier stored in ImDrawCmd. ImDrawCmd can refer to textures not created by the backend, and for which there's no ImTextureData.
// - void* BackendUserData = higher-level opaque storage for backend own book-keeping. Some backends may have enough with TexID and not need both.
// In columns below: who reads/writes each fields? 'r'=read, 'w'=write, 'core'=main library, 'backend'=renderer backend
struct ImTextureData
{
ImTextureStatus Status; // ImTextureStatus_OK/_WantCreate/_WantUpdates/_WantDestroy. Always use SetStatus() to modify!
ImTextureFormat Format; // ImTextureFormat_RGBA32 (default) or ImTextureFormat_Alpha8
int Width; // Texture width
int Height; // Texture height
int BytesPerPixel; // 4 or 1
int UniqueID; // Sequential index to facilitate identifying a texture when debugging/printing. Only unique per atlas.
unsigned char* Pixels; // Pointer to buffer holding 'Width*Height' pixels and 'Width*Height*BytesPerPixels' bytes.
ImTextureID TexID; // Always use SetTexID() to modify! Identifier stored in ImDrawCmd::GetTexID() and passed to backend RenderDrawData loop.
void* BackendUserData; // Convenience storage for backend. Some backends may have enough with TexID.
ImTextureRect UsedRect; // Bounding box encompassing all past and queued Updates[].
ImTextureRect UpdateRect; // Bounding box encompassing all queued Updates[].
ImVector<ImTextureRect> Updates; // Array of individual updates.
int UnusedFrames; // In order to facilitate handling Status==WantDestroy in some backend: this is a count successive frames where the texture was not used. Always >0 when Status==WantDestroy.
unsigned short RefCount; // Number of contexts using this texture.
bool UseColors; // Tell whether our texture data is known to use colors (rather than just white + alpha).
bool WantDestroyNextFrame; // [Internal] Queued to set ImTextureStatus_WantDestroy next frame. May still be used in the current frame.
//------------------------------------------ core / backend ---------------------------------------
int UniqueID; // w - // Sequential index to facilitate identifying a texture when debugging/printing. Unique per atlas.
ImTextureStatus Status; // rw rw // ImTextureStatus_OK/_WantCreate/_WantUpdates/_WantDestroy. Always use SetStatus() to modify!
void* BackendUserData; // - rw // Convenience storage for backend. Some backends may have enough with TexID.
ImTextureID TexID; // r w // Backend-specific texture identifier. Always use SetTexID() to modify! The identifier will stored in ImDrawCmd::GetTexID() and passed to backend's RenderDrawData function.
ImTextureFormat Format; // w r // ImTextureFormat_RGBA32 (default) or ImTextureFormat_Alpha8
int Width; // w r // Texture width
int Height; // w r // Texture height
int BytesPerPixel; // w r // 4 or 1
unsigned char* Pixels; // w r // Pointer to buffer holding 'Width*Height' pixels and 'Width*Height*BytesPerPixels' bytes.
ImTextureRect UsedRect; // w r // Bounding box encompassing all past and queued Updates[].
ImTextureRect UpdateRect; // w r // Bounding box encompassing all queued Updates[].
ImVector<ImTextureRect> Updates; // w r // Array of individual updates.
int UnusedFrames; // w r // In order to facilitate handling Status==WantDestroy in some backend: this is a count successive frames where the texture was not used. Always >0 when Status==WantDestroy.
unsigned short RefCount; // w r // Number of contexts using this texture. Used during backend shutdown.
bool UseColors; // w r // Tell whether our texture data is known to use colors (rather than just white + alpha).
bool WantDestroyNextFrame; // rw - // [Internal] Queued to set ImTextureStatus_WantDestroy next frame. May still be used in the current frame.
// Functions
ImTextureData() { memset(this, 0, sizeof(*this)); }