Fonts: proof of concept support for user textures.

# Conflicts:
#	imgui.h
#	imgui_internal.h

imgui.cpp

@@ -5231,6 +5231,8 @@ static void ImGui::UpdateTexturesEndFrame()
             tex->RefCount = (unsigned short)atlas->RefCount;
             g.PlatformIO.Textures.push_back(tex);
         }
+    for (ImTextureData* tex : g.UserTextures)
+        g.PlatformIO.Textures.push_back(tex);
 }
 
 // Called once a frame. Followed by SetCurrentFont() which sets up the remaining data.
@@ -8613,6 +8615,19 @@ void ImGui::UpdateFontsEndFrame()
     PopFont();
 }
 
+void ImGui::RegisterUserTexture(ImTextureData* tex)
+{
+    ImGuiContext& g = *GImGui;
+    IM_ASSERT(tex->RefCount > 0);
+    g.UserTextures.push_back(tex);
+}
+
+void ImGui::UnregisterUserTexture(ImTextureData* tex)
+{
+    ImGuiContext& g = *GImGui;
+    g.UserTextures.find_erase(tex);
+}
+
 void ImGui::RegisterFontAtlas(ImFontAtlas* atlas)
 {
     ImGuiContext& g = *GImGui;

imgui.h

@@ -3905,7 +3905,7 @@ struct ImGuiPlatformIO
 
     // Textures list (the list is updated by calling ImGui::EndFrame or ImGui::Render)
     // The ImGui_ImplXXXX_RenderDrawData() function of each backend generally access this via ImDrawData::Textures which points to this. The array is available here mostly because backends will want to destroy textures on shutdown.
-    ImVector<ImTextureData*>        Textures;           // List of textures used by Dear ImGui (most often 1).
+    ImVector<ImTextureData*>        Textures;           // List of textures used by Dear ImGui (most often 1) + contents of external texture list is automatically appended into this.
 };
 
 // (Optional) Support for IME (Input Method Editor) via the platform_io.Platform_SetImeDataFn() function. Handler is called during EndFrame().

imgui_internal.h

@@ -2426,6 +2426,10 @@ struct ImGuiContext
     ImGuiPlatformImeData    PlatformImeData;                    // Data updated by current frame. Will be applied at end of the frame. For some backends, this is required to have WantVisible=true in order to receive text message.
     ImGuiPlatformImeData    PlatformImeDataPrev;                // Previous frame data. When changed we call the platform_io.Platform_SetImeDataFn() handler.
 
+    // Extensions
+    // FIXME: We could provide an API to register one slot in an array held in ImGuiContext?
+    ImVector<ImTextureData*> UserTextures;                      // List of textures created/managed by user or third-party extension. Automatically appended into platform_io.Textures[].
+
     // Settings
     bool                    SettingsLoaded;
     float                   SettingsDirtyTimer;                 // Save .ini Settings to memory when time reaches zero
@@ -3108,6 +3112,8 @@ namespace ImGui
     IMGUI_API void          SetNextWindowRefreshPolicy(ImGuiWindowRefreshFlags flags);
 
     // Fonts, drawing
+    IMGUI_API void          RegisterUserTexture(ImTextureData* tex); // Register external texture
+    IMGUI_API void          UnregisterUserTexture(ImTextureData* tex);
     IMGUI_API void          RegisterFontAtlas(ImFontAtlas* atlas);
     IMGUI_API void          UnregisterFontAtlas(ImFontAtlas* atlas);
     IMGUI_API void          SetCurrentFont(ImFont* font, float font_size);