(Breaking) Fonts: PushFont() default to preserve current font size.

imgui.cpp

@@ -8582,7 +8582,7 @@ void ImGui::UpdateFontsNewFrame()
         atlas->Locked = true;
 
     // We do this really unusual thing of calling *push_front()*, the reason behind that we want to support the PushFont()/NewFrame()/PopFont() idiom.
-    ImFontStackData font_stack_data = { ImGui::GetDefaultFont(), ImGui::GetDefaultFont()->Sources[0].SizePixels };
+    ImFontStackData font_stack_data = { ImGui::GetDefaultFont(), ImGui::GetDefaultFont()->DefaultSize };
     g.FontStack.push_front(font_stack_data);
     if (g.FontStack.Size == 1)
         ImGui::SetCurrentFont(font_stack_data.Font, font_stack_data.FontSize);
@@ -8647,8 +8647,13 @@ void ImGui::PushFont(ImFont* font, float font_size)
     ImGuiContext& g = *GImGui;
     if (font == NULL)
         font = GetDefaultFont();
-    if (font_size < 0.0f)
-        font_size = font->Sources[0].SizePixels; // g.FontSize;
+    if (font_size <= 0.0f)
+    {
+        if (font->Flags & ImFontFlags_UseDefaultSize)
+            font_size = font->DefaultSize;       // Legacy: use default font size. Same as doing PushFont(font, font->DefaultSize). // FIXME-NEWATLAS
+        else
+            font_size = g.FontSizeBeforeScaling; // Keep current font size
+    }
     g.FontStack.push_back({ font, font_size });
     SetCurrentFont(font, font_size);
 }

imgui.h

@@ -491,9 +491,13 @@ namespace ImGui
     IMGUI_API void          SetScrollFromPosY(float local_y, float center_y_ratio = 0.5f);  // adjust scrolling amount to make given position visible. Generally GetCursorStartPos() + offset to compute a valid position.
 
     // Parameters stacks (font)
-    IMGUI_API void          PushFont(ImFont* font, float font_size = -1);                   // use NULL as a shortcut to push default font. Use <0.0f to keep current font size.
+    // *IMPORTANT* before 1.92, fonts had a single size. They can now be dynamically be adjusted.
+    // - Before 1.92: PushFont() always used font default size.
+    // -  Since 1.92: PushFont() preserve the current shared font size.
+    // - To use old behavior: use 'PushFont(font, font->DefaultSize)' in call site, or set 'ImFontConfig::Flags |= ImFontFlags_UseDefaultSize' before calling AddFont().
+    IMGUI_API void          PushFont(ImFont* font, float font_size = -1);                   // use NULL as a shortcut to push default font. Use <0.0f to keep current font size. Use font->DefaultSize to revert to font default size.
     IMGUI_API void          PopFont();
-    IMGUI_API void          PushFontSize(float size);
+    IMGUI_API void          PushFontSize(float font_size);
     IMGUI_API void          PopFontSize();
 
     // Parameters stacks (shared)
@@ -3709,6 +3713,7 @@ enum ImFontFlags_
     ImFontFlags_LockBakedSizes          = 1 << 0,   // Disable loading new baked sizes, disable garbage collecting current ones. e.g. if you want to lock a font to a single size.
     ImFontFlags_NoLoadGlyphs            = 1 << 1,   // Disable loading new glyphs.
     ImFontFlags_NoLoadError             = 1 << 2,   // Disable throwing an error/assert when calling AddFontXXX() with missing file/data. Calling code is expected to check AddFontXXX() return value.
+    ImFontFlags_UseDefaultSize          = 1 << 3,   // Legacy compatibility: make PushFont() calls without explicit size use font->DefaultSize instead of current font size.
 };
 
 // Font runtime data and rendering
@@ -3726,6 +3731,7 @@ struct ImFont
     // [Internal] Members: Cold ~24-52 bytes
     // Conceptually Sources[] is the list of font sources merged to create this font.
     ImGuiID                     FontId;             // Unique identifier for the font
+    float                       DefaultSize;        // 4     // in  // Default font size
     short                       SourcesCount;       // 2     // in  // Number of ImFontConfig involved in creating this font. Usually 1, or >1 when merging multiple font sources into one ImFont.
     ImFontConfig*               Sources;            // 4-8   // in  // Pointer within ContainerAtlas->Sources[], to SourcesCount instances
     ImWchar                     EllipsisChar;       // 2-4   // out // Character used for ellipsis rendering ('...').
@@ -3750,7 +3756,7 @@ struct ImFont
     IMGUI_API void              RenderChar(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, ImWchar c, const ImVec4* cpu_fine_clip = NULL);
     IMGUI_API void              RenderText(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, const ImVec4& clip_rect, const char* text_begin, const char* text_end, float wrap_width = 0.0f, bool cpu_fine_clip = false);
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
-    inline const char*          CalcWordWrapPositionA(float scale, const char* text, const char* text_end, float wrap_width) { return CalcWordWrapPosition(Sources[0].SizePixels * scale, text, text_end, wrap_width); }
+    inline const char*          CalcWordWrapPositionA(float scale, const char* text, const char* text_end, float wrap_width) { return CalcWordWrapPosition(DefaultSize * scale, text, text_end, wrap_width); }
 #endif
 
     // [Internal] Don't use!

imgui_draw.cpp

@@ -3005,6 +3005,7 @@ ImFont* ImFontAtlas::AddFont(const ImFontConfig* font_cfg)
         font = IM_NEW(ImFont)();
         font->FontId = FontNextUniqueID++;
         font->Flags = font_cfg->Flags;
+        font->DefaultSize = font_cfg->SizePixels;
         Fonts.push_back(font);
     }
     else
@@ -3248,7 +3249,7 @@ int ImFontAtlas::AddCustomRectRegular(int width, int height)
 //     myfont->Flags |= ImFontFlags_LockBakedSizes;
 int ImFontAtlas::AddCustomRectFontGlyph(ImFont* font, ImWchar codepoint, int width, int height, float advance_x, const ImVec2& offset)
 {
-    float font_size = font->Sources[0].SizePixels;
+    float font_size = font->DefaultSize;
     return AddCustomRectFontGlyphForSize(font, font_size, codepoint, width, height, advance_x, offset);
 }
 // FIXME: we automatically set glyph.Colored=true by default.