Fonts: added ImFontAtlas::SetFontLoader() to dynamically change font loader at runtime without using internal API. (#8752, #8465)

docs/CHANGELOG.txt

@@ -43,6 +43,8 @@ Breaking changes:
 
 Other changes:
 
+- Fonts: added ImFontAtlas::SetFontLoader() to dynamically change font
+  loader at runtime without using internal API. (#8752, #8465)
 - Textures: Fixed support for `#define ImTextureID_Invalid` to non-zero value:
   ImTextureData() was incorrectly cleared with zeroes. (#8745) [@rachit7645]
 - Demo: Added "Text -> Font Size" demo section. (#8738) [@Demonese]
@@ -211,7 +213,7 @@ Breaking changes:
      - renamed/reworked ImFontBuilderIO into ImFontLoader,
      - renamed ImGuiFreeType::GetBuilderForFreeType() to ImGuiFreeType::GetFontLoader()
        - old:  io.Fonts->FontBuilderIO = ImGuiFreeType::GetBuilderForFreeType()
-       - new:  io.Fonts.FontLoader = ImGuiFreeType::GetFontLoader();
+       - new:  io.Fonts->FontLoader = ImGuiFreeType::GetFontLoader()
 - DrawList: Renamed ImDrawList::PushTextureID()/PopTextureID() to PushTexture()/PopTexture().
 - Fonts: (users of custom rectangles)
   - Renamed AddCustomRectRegular() to AddCustomRect(). (#8466)

imgui.cpp

@@ -453,7 +453,8 @@ IMPLEMENTING SUPPORT for ImGuiBackendFlags_RendererHasTextures:
                        - Fonts: (users of imgui_freetype): renamed ImFontAtlas::FontBuilderFlags to ImFontAtlas::FontLoaderFlags. Renamed ImFontConfig::FontBuilderFlags to ImFontConfig::FontLoaderFlags. Renamed ImGuiFreeTypeBuilderFlags to ImGuiFreeTypeLoaderFlags.
                          If you used runtime imgui_freetype selection rather than the default IMGUI_ENABLE_FREETYPE compile-time option: Renamed/reworked ImFontBuilderIO into ImFontLoader. Renamed ImGuiFreeType::GetBuilderForFreeType() to ImGuiFreeType::GetFontLoader().
                            - old:  io.Fonts->FontBuilderIO = ImGuiFreeType::GetBuilderForFreeType()
-                           - new:  io.Fonts.FontLoader = ImGuiFreeType::GetFontLoader()
+                           - new:  io.Fonts->FontLoader = ImGuiFreeType::GetFontLoader()
+                           - new:  io.Fonts->SetFontLoader(ImGuiFreeType::GetFontLoader()) to change dynamically at runtime [from 1.92.1]
                        - Fonts: (users of custom rectangles, see #8466): Renamed AddCustomRectRegular() to AddCustomRect(). Added GetCustomRect() as a replacement for GetCustomRectByIndex() + CalcCustomRectUV().
                            - The output type of GetCustomRect() is now ImFontAtlasRect, which include UV coordinates. X->x, Y->y, Width->w, Height->h.
                            - old:
@@ -15902,7 +15903,7 @@ void ImGui::ShowFontAtlas(ImFontAtlas* atlas)
 #ifdef IMGUI_ENABLE_STB_TRUETYPE
         const ImFontLoader* loader_stbtruetype = ImFontAtlasGetFontLoaderForStbTruetype();
         if (RadioButton("stb_truetype", loader_current == loader_stbtruetype))
-            ImFontAtlasBuildSetupFontLoader(atlas, loader_stbtruetype);
+            atlas->SetFontLoader(loader_stbtruetype);
 #else
         BeginDisabled();
         RadioButton("stb_truetype", false);
@@ -15913,7 +15914,7 @@ void ImGui::ShowFontAtlas(ImFontAtlas* atlas)
 #ifdef IMGUI_ENABLE_FREETYPE
         const ImFontLoader* loader_freetype = ImGuiFreeType::GetFontLoader();
         if (RadioButton("FreeType", loader_current == loader_freetype))
-            ImFontAtlasBuildSetupFontLoader(atlas, loader_freetype);
+            atlas->SetFontLoader(loader_freetype);
         if (loader_current == loader_freetype)
         {
             unsigned int loader_flags = atlas->FontLoaderFlags;

imgui.h

@@ -3493,7 +3493,7 @@ struct ImFontConfig
     // [Internal]
     ImFontFlags     Flags;                  // Font flags (don't use just yet, will be exposed in upcoming 1.92.X updates)
     ImFont*         DstFont;                // Target font (as we merging fonts, multiple ImFontConfig may target the same font)
-    const ImFontLoader* FontLoader;         // Custom font backend for this source (other use one stored in ImFontAtlas)
+    const ImFontLoader* FontLoader;         // Custom font backend for this source (default source is the one stored in ImFontAtlas)
     void*           FontLoaderData;         // Font loader opaque storage (per font config)
 
     IMGUI_API ImFontConfig();
@@ -3590,6 +3590,7 @@ struct ImFontAtlas
 
     IMGUI_API void              Clear();                    // Clear everything (input fonts, output glyphs/textures)
     IMGUI_API void              CompactCache();             // Compact cached glyphs and texture.
+    IMGUI_API void              SetFontLoader(const ImFontLoader* font_loader); // Change font loader at runtime.
 
     // As we are transitioning toward a new font system, we expect to obsolete those soon:
     IMGUI_API void              ClearInputData();           // [OBSOLETE] Clear input data (all ImFontConfig structures including sizes, TTF data, glyph ranges, etc.) = all the data used to build the texture and fonts.
@@ -3698,7 +3699,7 @@ struct ImFontAtlas
     int                         FontNextUniqueID;   // Next value to be stored in ImFont->FontID
     ImVector<ImDrawListSharedData*> DrawListSharedDatas; // List of users for this atlas. Typically one per Dear ImGui context.
     ImFontAtlasBuilder*         Builder;            // Opaque interface to our data that doesn't need to be public and may be discarded when rebuilding.
-    const ImFontLoader*         FontLoader;         // Font loader opaque interface (default to stb_truetype, can be changed to use FreeType by defining IMGUI_ENABLE_FREETYPE). Don't set directly!
+    const ImFontLoader*         FontLoader;         // Font loader opaque interface (default to use FreeType when IMGUI_ENABLE_FREETYPE is defined, otherwise default to use stb_truetype). Use SetFontLoader() to change this at runtime.
     const char*                 FontLoaderName;     // Font loader name (for display e.g. in About box) == FontLoader->Name
     void*                       FontLoaderData;     // Font backend opaque storage
     unsigned int                FontLoaderFlags;    // Shared flags (for all fonts) for font loader. THIS IS BUILD IMPLEMENTATION DEPENDENT (e.g. Per-font override is also available in ImFontConfig).

imgui_draw.cpp

@@ -2659,6 +2659,11 @@ void ImFontAtlas::CompactCache()
     ImFontAtlasTextureCompact(this);
 }
 
+void ImFontAtlas::SetFontLoader(const ImFontLoader* font_loader)
+{
+    ImFontAtlasBuildSetupFontLoader(this, font_loader);
+}
+
 void ImFontAtlas::ClearInputData()
 {
     IM_ASSERT(!Locked && "Cannot modify a locked ImFontAtlas!");
@@ -4178,9 +4183,9 @@ void ImFontAtlasBuildInit(ImFontAtlas* atlas)
     if (atlas->FontLoader == NULL)
     {
 #ifdef IMGUI_ENABLE_FREETYPE
-        ImFontAtlasBuildSetupFontLoader(atlas, ImGuiFreeType::GetFontLoader());
+        atlas->SetFontLoader(ImGuiFreeType::GetFontLoader());
 #elif defined(IMGUI_ENABLE_STB_TRUETYPE)
-        ImFontAtlasBuildSetupFontLoader(atlas, ImFontAtlasGetFontLoaderForStbTruetype());
+        atlas->SetFontLoader(ImFontAtlasGetFontLoaderForStbTruetype());
 #else
         IM_ASSERT(0); // Invalid Build function
 #endif

misc/freetype/imgui_freetype.h

@@ -8,7 +8,7 @@
 // Usage:
 // - Add '#define IMGUI_ENABLE_FREETYPE' in your imconfig to automatically enable support
 //   for imgui_freetype in imgui. It is equivalent to selecting the default loader with:
-//      io.Fonts.FontLoader = ImGuiFreeType::GetFontLoader()
+//      io.Fonts->SetFontLoader(ImGuiFreeType::GetFontLoader())
 
 // Optional support for OpenType SVG fonts:
 // - Add '#define IMGUI_ENABLE_FREETYPE_PLUTOSVG' to use plutosvg (not provided). See #7927.
@@ -62,7 +62,7 @@ namespace ImGuiFreeType
 {
     // This is automatically assigned when using '#define IMGUI_ENABLE_FREETYPE'.
     // If you need to dynamically select between multiple builders:
-    // - you can manually assign this builder with 'atlas->FontLoader = ImGuiFreeType::GetFontLoader()'
+    // - you can manually assign this builder with 'atlas->SetFontLoader(ImGuiFreeType::GetFontLoader())'
     // - prefer deep-copying this into your own ImFontLoader instance if you use hot-reloading that messes up static data.
     IMGUI_API const ImFontLoader*       GetFontLoader();
 
@@ -75,7 +75,7 @@ namespace ImGuiFreeType
 
     // Obsolete names (will be removed)
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
-    //IMGUI_API const ImFontBuilderIO* GetBuilderForFreeType(); // Renamed/changed in 1.92. Change 'io.Fonts->FontBuilderIO = ImGuiFreeType::GetBuilderForFreeType()' to 'io.Fonts.FontLoader = ImGuiFreeType::GetFontLoader()' if you need runtime selection.
+    //IMGUI_API const ImFontBuilderIO* GetBuilderForFreeType(); // Renamed/changed in 1.92. Change 'io.Fonts->FontBuilderIO = ImGuiFreeType::GetBuilderForFreeType()' to 'io.Fonts->SetFontLoader(ImGuiFreeType::GetFontLoader())' if you need runtime selection.
     //static inline bool BuildFontAtlas(ImFontAtlas* atlas, unsigned int flags = 0) { atlas->FontBuilderIO = GetBuilderForFreeType(); atlas->FontLoaderFlags = flags; return atlas->Build(); } // Prefer using '#define IMGUI_ENABLE_FREETYPE'
 #endif
 }