Windows: legacy SetWindowFontScale() is properly inherited by nested child windows. (#2701, #8138, #1018)

docs/CHANGELOG.txt

@@ -51,6 +51,9 @@ Other changes:
   snapped to pixels. Effectively it would only be noticeable when hinting
   is disabled with ImGuiFreeTypeBuilderFlags_NoHinting, as hinting itself
   snaps glyph advances.
+- Windows: legacy SetWindowFontScale() is properly inherited by nested child
+  windows. Note that an upcoming major release should make this obsolete,
+  but in the meanwhile it works better now. (#2701, #8138, #1018)
 - Examples: DirectX12: Reduced number of frame in flight from 3 to 2 in
   provided example, to reduce latency.
 - Examples: Vulkan: better handle VK_SUBOPTIMAL_KHR being returned by

imgui.cpp

@@ -4276,7 +4276,7 @@ ImGuiWindow::ImGuiWindow(ImGuiContext* ctx, const char* name) : DrawListInst(NUL
     SetWindowPosVal = SetWindowPosPivot = ImVec2(FLT_MAX, FLT_MAX);
     LastFrameActive = -1;
     LastTimeActive = -1.0f;
-    FontWindowScale = 1.0f;
+    FontWindowScale = FontWindowScaleParents = 1.0f;
     SettingsOffset = -1;
     DrawList = &DrawListInst;
     DrawList->_OwnerName = Name;
@@ -7037,6 +7037,9 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // There's little point to expose a flag to set this: because the interesting cases won't be using parent_window_in_stack,
         // e.g. linking a tool window in a standalone viewport to a document window, regardless of their Begin() stack parenting. (#6798)
         window->ParentWindowForFocusRoute = (flags & ImGuiWindowFlags_ChildWindow) ? parent_window_in_stack : NULL;
+
+        // Inherent SetWindowFontScale() from parent until we fix this system...
+        window->FontWindowScaleParents = parent_window ? parent_window->FontWindowScaleParents * parent_window->FontWindowScale : 1.0f;
     }
 
     // Add to focus scope stack

imgui.h

@@ -29,7 +29,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.91.8 WIP"
-#define IMGUI_VERSION_NUM   19171
+#define IMGUI_VERSION_NUM   19172
 #define IMGUI_HAS_TABLE
 
 /*

imgui_internal.h

@@ -2551,6 +2551,7 @@ struct IMGUI_API ImGuiWindow
     ImGuiStorage            StateStorage;
     ImVector<ImGuiOldColumns> ColumnsStorage;
     float                   FontWindowScale;                    // User scale multiplier per-window, via SetWindowFontScale()
+    float                   FontWindowScaleParents;
     int                     SettingsOffset;                     // Offset into SettingsWindows[] (offsets are always valid as we only grow the array from the back)
 
     ImDrawList*             DrawList;                           // == &DrawListInst (for backward compatibility reason with code using imgui_internal.h we keep this a pointer)
@@ -2585,7 +2586,7 @@ public:
 
     // We don't use g.FontSize because the window may be != g.CurrentWindow.
     ImRect      Rect() const            { return ImRect(Pos.x, Pos.y, Pos.x + Size.x, Pos.y + Size.y); }
-    float       CalcFontSize() const    { ImGuiContext& g = *Ctx; float scale = g.FontBaseSize * FontWindowScale; if (ParentWindow) scale *= ParentWindow->FontWindowScale; return scale; }
+    float       CalcFontSize() const    { ImGuiContext& g = *Ctx; return g.FontBaseSize * FontWindowScale * FontWindowScaleParents; }
     ImRect      TitleBarRect() const    { return ImRect(Pos, ImVec2(Pos.x + SizeFull.x, Pos.y + TitleBarHeight)); }
     ImRect      MenuBarRect() const     { float y1 = Pos.y + TitleBarHeight; return ImRect(Pos.x, y1, Pos.x + SizeFull.x, y1 + MenuBarHeight); }
 };