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Backends: GLFW: Added support for multiple Dear ImGui contexts. (#8676, #8239, #8069)

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ocornut
2025-06-18 16:40:35 +02:00
parent d290e583c5
commit f633a60581
3 changed files with 62 additions and 43 deletions
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102
backends/imgui_impl_glfw.cpp
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@@ -9,6 +9,7 @@
// [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy GLFW_KEY_* values are obsolete since 1.87 and not supported since 1.91.5]
// [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
// [X] Platform: Mouse cursor shape and visibility (ImGuiBackendFlags_HasMouseCursors). Resizing cursors requires GLFW 3.4+! Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
// [X] Multiple Dear ImGui contexts support.
// Missing features or Issues:
// [ ] Touch events are only correctly identified as Touch on Windows. This create issues with some interactions. GLFW doesn't provide a way to identify touch inputs from mouse inputs, we cannot call io.AddMouseSourceEvent() to identify the source. We provide a Windows-specific workaround.
// [ ] Missing ImGuiMouseCursor_Wait and ImGuiMouseCursor_Progress cursors.
@@ -28,6 +29,7 @@
// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
// 2025-06-18: Added support for multiple Dear ImGui contexts. (#8676, #8239, #8069)
// 2025-06-11: Added ImGui_ImplGlfw_GetContentScaleForWindow(GLFWwindow* window) and ImGui_ImplGlfw_GetContentScaleForMonitor(GLFWmonitor* monitor) helper to facilitate making DPI-aware apps.
// 2025-03-10: Map GLFW_KEY_WORLD_1 and GLFW_KEY_WORLD_2 into ImGuiKey_Oem102.
// 2025-03-03: Fixed clipboard handler assertion when using GLFW <= 3.2.1 compiled with asserts enabled.
@@ -141,6 +143,16 @@
#define GLFW_HAS_GETKEYNAME (GLFW_VERSION_COMBINED >= 3200) // 3.2+ glfwGetKeyName()
#define GLFW_HAS_GETERROR (GLFW_VERSION_COMBINED >= 3300) // 3.3+ glfwGetError()
// Map GLFWWindow* to ImGuiContext*.
// - Would be simpler if we could use glfwSetWindowUserPointer()/glfwGetWindowUserPointer(), but this is a single and shared resource.
// - Would be simpler if we could use e.g. std::map<> as well. But we don't.
// - This is not particularly optimized as we expect size to be small and queries to be rare.
struct ImGui_ImplGlfw_WindowToContext { GLFWwindow* Window; ImGuiContext* Context; };
static ImVector<ImGui_ImplGlfw_WindowToContext> g_ContextMap;
static void ImGui_ImplGlfw_ContextMap_Add(GLFWwindow* window, ImGuiContext* ctx) { g_ContextMap.push_back(ImGui_ImplGlfw_WindowToContext{ window, ctx }); }
static void ImGui_ImplGlfw_ContextMap_Remove(GLFWwindow* window) { for (ImGui_ImplGlfw_WindowToContext& entry : g_ContextMap) if (entry.Window == window) { g_ContextMap.erase_unsorted(&entry); return; } }
static ImGuiContext* ImGui_ImplGlfw_ContextMap_Get(GLFWwindow* window) { for (ImGui_ImplGlfw_WindowToContext& entry : g_ContextMap) if (entry.Window == window) return entry.Context; return nullptr; }
// GLFW data
enum GlfwClientApi
{
@@ -151,6 +163,7 @@ enum GlfwClientApi
struct ImGui_ImplGlfw_Data
{
ImGuiContext* Context;
GLFWwindow* Window;
GlfwClientApi ClientApi;
double Time;
@@ -187,13 +200,17 @@ struct ImGui_ImplGlfw_Data
// (passing install_callbacks=false in ImGui_ImplGlfw_InitXXX functions), set the current dear imgui context and then call our callbacks.
// - Otherwise we may need to store a GLFWWindow* -> ImGuiContext* map and handle this in the backend, adding a little bit of extra complexity to it.
// FIXME: some shared resources (mouse cursor shape, gamepad) are mishandled when using multi-context.
namespace ImGui { extern ImGuiIO& GetIO(ImGuiContext*); }
static ImGui_ImplGlfw_Data* ImGui_ImplGlfw_GetBackendData()
{
// Get data for current context
return ImGui::GetCurrentContext() ? (ImGui_ImplGlfw_Data*)ImGui::GetIO().BackendPlatformUserData : nullptr;
}
static ImGui_ImplGlfw_Data* ImGui_ImplGlfw_GetBackendData(ImGuiIO& io)
static ImGui_ImplGlfw_Data* ImGui_ImplGlfw_GetBackendData(GLFWwindow* window)
{
return (ImGui_ImplGlfw_Data*)io.BackendPlatformUserData;
// Get data for a given GLFW window, regardless of current context (since GLFW events are sent together)
ImGuiContext* ctx = ImGui_ImplGlfw_ContextMap_Get(window);
return (ImGui_ImplGlfw_Data*)ImGui::GetIO(ctx).BackendPlatformUserData;
}
// Functions
@@ -330,38 +347,36 @@ ImGuiKey ImGui_ImplGlfw_KeyToImGuiKey(int keycode, int scancode)
// X11 does not include current pressed/released modifier key in 'mods' flags submitted by GLFW
// See https://github.com/ocornut/imgui/issues/6034 and https://github.com/glfw/glfw/issues/1630
static void ImGui_ImplGlfw_UpdateKeyModifiers(GLFWwindow* window)
static void ImGui_ImplGlfw_UpdateKeyModifiers(ImGuiIO& io, GLFWwindow* window)
{
ImGuiIO& io = ImGui::GetIO();
io.AddKeyEvent(ImGuiMod_Ctrl, (glfwGetKey(window, GLFW_KEY_LEFT_CONTROL) == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_CONTROL) == GLFW_PRESS));
io.AddKeyEvent(ImGuiMod_Shift, (glfwGetKey(window, GLFW_KEY_LEFT_SHIFT) == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_SHIFT) == GLFW_PRESS));
io.AddKeyEvent(ImGuiMod_Alt, (glfwGetKey(window, GLFW_KEY_LEFT_ALT) == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_ALT) == GLFW_PRESS));
io.AddKeyEvent(ImGuiMod_Super, (glfwGetKey(window, GLFW_KEY_LEFT_SUPER) == GLFW_PRESS) || (glfwGetKey(window, GLFW_KEY_RIGHT_SUPER) == GLFW_PRESS));
}
static bool ImGui_ImplGlfw_ShouldChainCallback(GLFWwindow* window)
static bool ImGui_ImplGlfw_ShouldChainCallback(ImGui_ImplGlfw_Data* bd, GLFWwindow* window)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
return bd->CallbacksChainForAllWindows ? true : (window == bd->Window);
}
void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow* window, int button, int action, int mods)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
if (bd->PrevUserCallbackMousebutton != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
if (bd->PrevUserCallbackMousebutton != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
bd->PrevUserCallbackMousebutton(window, button, action, mods);
ImGui_ImplGlfw_UpdateKeyModifiers(window);
ImGuiIO& io = ImGui::GetIO();
ImGuiIO& io = ImGui::GetIO(bd->Context);
ImGui_ImplGlfw_UpdateKeyModifiers(io, window);
if (button >= 0 && button < ImGuiMouseButton_COUNT)
io.AddMouseButtonEvent(button, action == GLFW_PRESS);
}
void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yoffset)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
if (bd->PrevUserCallbackScroll != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
if (bd->PrevUserCallbackScroll != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
bd->PrevUserCallbackScroll(window, xoffset, yoffset);
#ifdef EMSCRIPTEN_USE_EMBEDDED_GLFW3
@@ -369,7 +384,7 @@ void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yo
return;
#endif
ImGuiIO& io = ImGui::GetIO();
ImGuiIO& io = ImGui::GetIO(bd->Context);
io.AddMouseWheelEvent((float)xoffset, (float)yoffset);
}
@@ -409,18 +424,18 @@ static int ImGui_ImplGlfw_TranslateUntranslatedKey(int key, int scancode)
void ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int keycode, int scancode, int action, int mods)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
if (bd->PrevUserCallbackKey != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
if (bd->PrevUserCallbackKey != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
bd->PrevUserCallbackKey(window, keycode, scancode, action, mods);
if (action != GLFW_PRESS && action != GLFW_RELEASE)
return;
ImGui_ImplGlfw_UpdateKeyModifiers(window);
ImGuiIO& io = ImGui::GetIO(bd->Context);
ImGui_ImplGlfw_UpdateKeyModifiers(io, window);
keycode = ImGui_ImplGlfw_TranslateUntranslatedKey(keycode, scancode);
ImGuiIO& io = ImGui::GetIO();
ImGuiKey imgui_key = ImGui_ImplGlfw_KeyToImGuiKey(keycode, scancode);
io.AddKeyEvent(imgui_key, (action == GLFW_PRESS));
io.SetKeyEventNativeData(imgui_key, keycode, scancode); // To support legacy indexing (<1.87 user code)
@@ -428,21 +443,21 @@ void ImGui_ImplGlfw_KeyCallback(GLFWwindow* window, int keycode, int scancode, i
void ImGui_ImplGlfw_WindowFocusCallback(GLFWwindow* window, int focused)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
if (bd->PrevUserCallbackWindowFocus != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
if (bd->PrevUserCallbackWindowFocus != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
bd->PrevUserCallbackWindowFocus(window, focused);
ImGuiIO& io = ImGui::GetIO();
ImGuiIO& io = ImGui::GetIO(bd->Context);
io.AddFocusEvent(focused != 0);
}
void ImGui_ImplGlfw_CursorPosCallback(GLFWwindow* window, double x, double y)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
if (bd->PrevUserCallbackCursorPos != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
if (bd->PrevUserCallbackCursorPos != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
bd->PrevUserCallbackCursorPos(window, x, y);
ImGuiIO& io = ImGui::GetIO();
ImGuiIO& io = ImGui::GetIO(bd->Context);
io.AddMousePosEvent((float)x, (float)y);
bd->LastValidMousePos = ImVec2((float)x, (float)y);
}
@@ -451,11 +466,11 @@ void ImGui_ImplGlfw_CursorPosCallback(GLFWwindow* window, double x, double y)
// so we back it up and restore on Leave/Enter (see https://github.com/ocornut/imgui/issues/4984)
void ImGui_ImplGlfw_CursorEnterCallback(GLFWwindow* window, int entered)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
if (bd->PrevUserCallbackCursorEnter != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
if (bd->PrevUserCallbackCursorEnter != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
bd->PrevUserCallbackCursorEnter(window, entered);
ImGuiIO& io = ImGui::GetIO();
ImGuiIO& io = ImGui::GetIO(bd->Context);
if (entered)
{
bd->MouseWindow = window;
@@ -471,11 +486,11 @@ void ImGui_ImplGlfw_CursorEnterCallback(GLFWwindow* window, int entered)
void ImGui_ImplGlfw_CharCallback(GLFWwindow* window, unsigned int c)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
if (bd->PrevUserCallbackChar != nullptr && ImGui_ImplGlfw_ShouldChainCallback(window))
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
if (bd->PrevUserCallbackChar != nullptr && ImGui_ImplGlfw_ShouldChainCallback(bd, window))
bd->PrevUserCallbackChar(window, c);
ImGuiIO& io = ImGui::GetIO();
ImGuiIO& io = ImGui::GetIO(bd->Context);
io.AddInputCharacter(c);
}
@@ -485,17 +500,18 @@ void ImGui_ImplGlfw_MonitorCallback(GLFWmonitor*, int)
}
#ifdef EMSCRIPTEN_USE_EMBEDDED_GLFW3
static EM_BOOL ImGui_ImplEmscripten_WheelCallback(int, const EmscriptenWheelEvent* ev, void*)
static EM_BOOL ImGui_ImplEmscripten_WheelCallback(int, const EmscriptenWheelEvent* ev, void* user_data)
{
// Mimic Emscripten_HandleWheel() in SDL.
// Corresponding equivalent in GLFW JS emulation layer has incorrect quantizing preventing small values. See #6096
ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data*)user_data;
float multiplier = 0.0f;
if (ev->deltaMode == DOM_DELTA_PIXEL) { multiplier = 1.0f / 100.0f; } // 100 pixels make up a step.
else if (ev->deltaMode == DOM_DELTA_LINE) { multiplier = 1.0f / 3.0f; } // 3 lines make up a step.
else if (ev->deltaMode == DOM_DELTA_PAGE) { multiplier = 80.0f; } // A page makes up 80 steps.
float wheel_x = ev->deltaX * -multiplier;
float wheel_y = ev->deltaY * -multiplier;
ImGuiIO& io = ImGui::GetIO();
ImGuiIO& io = ImGui::GetIO(bd->Context);
io.AddMouseWheelEvent(wheel_x, wheel_y);
//IMGUI_DEBUG_LOG("[Emsc] mode %d dx: %.2f, dy: %.2f, dz: %.2f --> feed %.2f %.2f\n", (int)ev->deltaMode, ev->deltaX, ev->deltaY, ev->deltaZ, wheel_x, wheel_y);
return EM_TRUE;
@@ -505,7 +521,6 @@ static EM_BOOL ImGui_ImplEmscripten_WheelCallback(int, const EmscriptenWheelEven
#ifdef _WIN32
// GLFW doesn't allow to distinguish Mouse vs TouchScreen vs Pen.
// Add support for Win32 (based on imgui_impl_win32), because we rely on _TouchScreen info to trickle inputs differently.
namespace ImGui { extern ImGuiIO& GetIO(ImGuiContext*); }
static ImGuiMouseSource GetMouseSourceFromMessageExtraInfo()
{
LPARAM extra_info = ::GetMessageExtraInfo();
@@ -517,10 +532,9 @@ static ImGuiMouseSource GetMouseSourceFromMessageExtraInfo()
}
static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
ImGuiContext* ctx = (ImGuiContext*)::GetPropA(hWnd, "IMGUI_CONTEXT");
ImGuiIO& io = ImGui::GetIO(ctx);
ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data*)::GetPropA(hWnd, "IMGUI_BACKEND_DATA");
ImGuiIO& io = ImGui::GetIO(bd->Context);
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(io);
switch (msg)
{
case WM_MOUSEMOVE: case WM_NCMOUSEMOVE:
@@ -537,7 +551,7 @@ static LRESULT CALLBACK ImGui_ImplGlfw_WndProc(HWND hWnd, UINT msg, WPARAM wPara
void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
IM_ASSERT(bd->InstalledCallbacks == false && "Callbacks already installed!");
IM_ASSERT(bd->Window == window);
@@ -554,7 +568,7 @@ void ImGui_ImplGlfw_InstallCallbacks(GLFWwindow* window)
void ImGui_ImplGlfw_RestoreCallbacks(GLFWwindow* window)
{
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData(window);
IM_ASSERT(bd->InstalledCallbacks == true && "Callbacks not installed!");
IM_ASSERT(bd->Window == window);
@@ -610,8 +624,10 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors; // We can honor GetMouseCursor() values (optional)
io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos; // We can honor io.WantSetMousePos requests (optional, rarely used)
bd->Context = ImGui::GetCurrentContext();
bd->Window = window;
bd->Time = 0.0;
ImGui_ImplGlfw_ContextMap_Add(window, bd->Context);
ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
#if GLFW_VERSION_COMBINED < 3300
@@ -669,8 +685,9 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
// Windows: register a WndProc hook so we can intercept some messages.
#ifdef _WIN32
::SetPropA((HWND)main_viewport->PlatformHandleRaw, "IMGUI_CONTEXT", ImGui::GetCurrentContext());
bd->PrevWndProc = (WNDPROC)::GetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC);
HWND hwnd = (HWND)main_viewport->PlatformHandleRaw;
::SetPropA(hwnd, "IMGUI_BACKEND_DATA", bd);
bd->PrevWndProc = (WNDPROC)::GetWindowLongPtrW(hwnd, GWLP_WNDPROC);
IM_ASSERT(bd->PrevWndProc != nullptr);
::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)ImGui_ImplGlfw_WndProc);
#endif
@@ -730,7 +747,7 @@ void ImGui_ImplGlfw_Shutdown()
// Windows: restore our WndProc hook
#ifdef _WIN32
ImGuiViewport* main_viewport = ImGui::GetMainViewport();
::SetPropA((HWND)main_viewport->PlatformHandleRaw, "IMGUI_CONTEXT", nullptr);
::SetPropA((HWND)main_viewport->PlatformHandleRaw, "IMGUI_BACKEND_DATA", nullptr);
::SetWindowLongPtrW((HWND)main_viewport->PlatformHandleRaw, GWLP_WNDPROC, (LONG_PTR)bd->PrevWndProc);
bd->PrevWndProc = nullptr;
#endif
@@ -738,6 +755,7 @@ void ImGui_ImplGlfw_Shutdown()
io.BackendPlatformName = nullptr;
io.BackendPlatformUserData = nullptr;
io.BackendFlags &= ~(ImGuiBackendFlags_HasMouseCursors | ImGuiBackendFlags_HasSetMousePos | ImGuiBackendFlags_HasGamepad);
ImGui_ImplGlfw_ContextMap_Remove(bd->Window);
IM_DELETE(bd);
}
@@ -961,7 +979,7 @@ void ImGui_ImplGlfw_InstallEmscriptenCallbacks(GLFWwindow*, const char* canvas_s
// Register Emscripten Wheel callback to workaround issue in Emscripten GLFW Emulation (#6096)
// We intentionally do not check 'if (install_callbacks)' here, as some users may set it to false and call GLFW callback themselves.
// FIXME: May break chaining in case user registered their own Emscripten callback?
emscripten_set_wheel_callback(bd->CanvasSelector, nullptr, false, ImGui_ImplEmscripten_WheelCallback);
emscripten_set_wheel_callback(bd->CanvasSelector, bd, false, ImGui_ImplEmscripten_WheelCallback);
}
#elif defined(EMSCRIPTEN_USE_PORT_CONTRIB_GLFW3)
// When using --use-port=contrib.glfw3 for the GLFW implementation, you can override the behavior of this call

1
backends/imgui_impl_glfw.h
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@@ -8,6 +8,7 @@
// [X] Platform: Keyboard support. Since 1.87 we are using the io.AddKeyEvent() function. Pass ImGuiKey values to all key functions e.g. ImGui::IsKeyPressed(ImGuiKey_Space). [Legacy GLFW_KEY_* values are obsolete since 1.87 and not supported since 1.91.5]
// [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
// [X] Platform: Mouse cursor shape and visibility (ImGuiBackendFlags_HasMouseCursors). Resizing cursors requires GLFW 3.4+! Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange'.
// [X] Multiple Dear ImGui contexts support.
// Missing features or Issues:
// [ ] Touch events are only correctly identified as Touch on Windows. This create issues with some interactions. GLFW doesn't provide a way to identify touch inputs from mouse inputs, we cannot call io.AddMouseSourceEvent() to identify the source. We provide a Windows-specific workaround.
// [ ] Missing ImGuiMouseCursor_Wait and ImGuiMouseCursor_Progress cursors.

2
docs/CHANGELOG.txt
View File

@@ -407,7 +407,7 @@ Other changes:
- Backends: GLFW: added ImGui_ImplGlfw_GetContentScaleForMonitor(), ImGui_ImplGlfw_GetContentScaleForWindow()
helpers. They are wrappers to glfwGetMonitorContentScale()/glfwGetWindowContentScale(), with compile-time
GLFW version checks + returning 1.0f on Apple platform.
- Backends: GLFW: fixed Win32 specific WndProc handler relying on current context. (#8676, #8239, #8069)
- Backends: GLFW: Added support for multiple Dear ImGui contexts. (#8676, #8239, #8069)
- Backends: SDL2: added ImGui_ImplSDL2_GetDpiScaleForDisplay() and ImGui_ImplSDL2_GetContentScaleForWindow()
helpers. They are wrappers to SDL_GetDisplayDPI(), with compile-time SDL version checks + returning 1.0f
on Apple platforms. SDL3 already does this by default.