Fonts: set a maximum font size of 512.0f at ImGui:: API level to reduce edge cases.

docs/CHANGELOG.txt

@@ -45,6 +45,9 @@ Other changes:
 
 - Fonts: added ImFontAtlas::SetFontLoader() to dynamically change font
   loader at runtime without using internal API. (#8752, #8465)
+- Fonts: set a maximum font size of 512.0f at ImGui:: API level to reduce
+  edge cases (e.g. out of memory errors). ImDrawList:: API doesn't have the
+  constraint. (#8758)
 - 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]

imgui.cpp

@@ -8824,7 +8824,7 @@ void ImGui::UpdateCurrentFontSize(float restore_font_size_after_scaling)
     // - We started rounding in 1.90 WIP (18991) as our layout system currently doesn't support non-rounded font size well yet.
     // - We may support it better later and remove this rounding.
     final_size = GetRoundedFontSize(final_size);
-    final_size = ImMax(1.0f, final_size);
+    final_size = ImClamp(final_size, 1.0f, IMGUI_FONT_SIZE_MAX);
     if (g.Font != NULL && (g.IO.BackendFlags & ImGuiBackendFlags_RendererHasTextures))
         g.Font->CurrentRasterizerDensity = g.FontRasterizerDensity;
     g.FontSize = final_size;
@@ -15871,9 +15871,9 @@ void ImGui::ShowFontAtlas(ImFontAtlas* atlas)
         style._NextFrameFontSizeBase = style.FontSizeBase; // FIXME: Temporary hack until we finish remaining work.
     SameLine(0.0f, 0.0f); Text(" (out %.2f)", GetFontSize());
     SameLine(); MetricsHelpMarker("- This is scaling font only. General scaling will come later.");
-    DragFloat("FontScaleMain", &style.FontScaleMain, 0.02f, 0.5f, 5.0f);
+    DragFloat("FontScaleMain", &style.FontScaleMain, 0.02f, 0.5f, 4.0f);
     //BeginDisabled(io.ConfigDpiScaleFonts);
-    DragFloat("FontScaleDpi", &style.FontScaleDpi, 0.02f, 0.5f, 5.0f);
+    DragFloat("FontScaleDpi", &style.FontScaleDpi, 0.02f, 0.5f, 4.0f);
     //SetItemTooltip("When io.ConfigDpiScaleFonts is set, this value is automatically overwritten.");
     //EndDisabled();
     if ((io.BackendFlags & ImGuiBackendFlags_RendererHasTextures) == 0)

imgui_demo.cpp

@@ -8282,7 +8282,7 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
         SameLine(0.0f, 0.0f); Text(" (out %.2f)", GetFontSize());
         DragFloat("FontScaleMain", &style.FontScaleMain, 0.02f, 0.5f, 4.0f);
         //BeginDisabled(GetIO().ConfigDpiScaleFonts);
-        DragFloat("FontScaleDpi", &style.FontScaleDpi, 0.02f, 0.5f, 5.0f);
+        DragFloat("FontScaleDpi", &style.FontScaleDpi, 0.02f, 0.5f, 4.0f);
         //SetItemTooltip("When io.ConfigDpiScaleFonts is set, this value is automatically overwritten.");
         //EndDisabled();
 

imgui_internal.h

@@ -3711,6 +3711,8 @@ typedef ImFontLoader ImFontBuilderIO; // [renamed/changed in 1.92] The types are
 // [SECTION] ImFontAtlas internal API
 //-----------------------------------------------------------------------------
 
+#define IMGUI_FONT_SIZE_MAX     (512.0f)
+
 // Helpers: ImTextureRef ==/!= operators provided as convenience
 // (note that _TexID and _TexData are never set simultaneously)
 inline bool operator==(const ImTextureRef& lhs, const ImTextureRef& rhs)    { return lhs._TexID == rhs._TexID && lhs._TexData == rhs._TexData; }