Modals: Temporary changes of ImGuiCol_ModalWindowDimBg are properly handled by BeginPopupModal(). (#7340)

+ Misc: Added optional alpha multiplier parameter to GetColorU32(ImU32) variant.

docs/CHANGELOG.txt

@@ -47,6 +47,8 @@ Other changes:
   erroneously close the window. (#7325, #7287, #7063)
 - Popups: Fixed resizable popup minimum size being too small. Standardized minimum
   size logic. (#7329).
+- Modals: Temporary changes of ImGuiCol_ModalWindowDimBg are properly handled by
+  BeginPopupModal(). (#7340)
 - Tables: Angled headers: fixed support for multi-line labels. (#6917)
 - Tables: Angled headers: various fixes to accurately handle CellPadding changes. (#6917)
 - Tables: Angled headers: properly registers horizontal component of angled headers
@@ -58,6 +60,7 @@ Other changes:
 - Debug Tools: Item Picker: Promoted ImGui::DebugStartItemPicker() to public API. (#2673)
 - Debug Tools: Item Picker: Menu entry visible in Demo->Tools but greyed out unless
   io.ConfigDebugIsDebuggerPresent is set. (#2673)
+- Misc: Added optional alpha multiplier parameter to GetColorU32(ImU32) variant.
 - Demo: Custom Rendering: better demonstrate PathArcTo(), PathBezierQuadraticCurveTo(),
   PathBezierCubicCurveTo(), PathStroke(), PathFillConvex() functions.
 
@@ -88,7 +91,7 @@ Other changes:
   Added ImGui_ImplSDL2_SetGamepadMode()) function to select whether to automatically pick
   first available gamepad, all gamepads, or specific gamepads.
   (#3884, #6559, #6890, #7180) [@ocornut, @lethal-guitar, @wn2000, @bog-dan-ro]
-- BackendsL SDL3: Fixed gamepad handling. (#7180) [@bog-dan-ro]
+- Backends: SDL3: Fixed gamepad handling. (#7180) [@bog-dan-ro]
 - Backends: SDLRenderer3: query newly added SDL_RenderViewportSet() to not restore
   a wrong viewport if none was initially set.
 - Backends: DirectX9: Using RGBA format when allowed by the driver to avoid CPU side

imgui.cpp

@@ -3047,13 +3047,14 @@ const ImVec4& ImGui::GetStyleColorVec4(ImGuiCol idx)
     return style.Colors[idx];
 }
 
-ImU32 ImGui::GetColorU32(ImU32 col)
+ImU32 ImGui::GetColorU32(ImU32 col, float alpha_mul)
 {
     ImGuiStyle& style = GImGui->Style;
-    if (style.Alpha >= 1.0f)
+    alpha_mul *= style.Alpha;
+    if (alpha_mul >= 1.0f)
         return col;
     ImU32 a = (col & IM_COL32_A_MASK) >> IM_COL32_A_SHIFT;
-    a = (ImU32)(a * style.Alpha); // We don't need to clamp 0..255 because Style.Alpha is in 0..1 range.
+    a = (ImU32)(a * alpha_mul); // We don't need to clamp 0..255 because alpha is in 0..1 range.
     return (col & ~IM_COL32_A_MASK) | (a << IM_COL32_A_SHIFT);
 }
 
@@ -5002,7 +5003,7 @@ static void ImGui::RenderDimmedBackgrounds()
     {
         // Draw dimming behind modal or a begin stack child, whichever comes first in draw order.
         ImGuiWindow* dim_behind_window = FindBottomMostVisibleWindowWithinBeginStack(modal_window);
-        RenderDimmedBackgroundBehindWindow(dim_behind_window, GetColorU32(ImGuiCol_ModalWindowDimBg, g.DimBgRatio));
+        RenderDimmedBackgroundBehindWindow(dim_behind_window, GetColorU32(modal_window->DC.ModalDimBgColor, g.DimBgRatio));
     }
     else if (dim_bg_for_window_list)
     {
@@ -6960,6 +6961,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->DC.TextWrapPos = -1.0f; // disabled
         window->DC.ItemWidthStack.resize(0);
         window->DC.TextWrapPosStack.resize(0);
+        if (flags & ImGuiWindowFlags_Modal)
+            window->DC.ModalDimBgColor = ColorConvertFloat4ToU32(GetStyleColorVec4(ImGuiCol_ModalWindowDimBg));
 
         if (window->AutoFitFramesX > 0)
             window->AutoFitFramesX--;

imgui.h

@@ -445,7 +445,7 @@ namespace ImGui
     IMGUI_API ImVec2        GetFontTexUvWhitePixel();                                       // get UV coordinate for a while pixel, useful to draw custom shapes via the ImDrawList API
     IMGUI_API ImU32         GetColorU32(ImGuiCol idx, float alpha_mul = 1.0f);              // retrieve given style color with style alpha applied and optional extra alpha multiplier, packed as a 32-bit value suitable for ImDrawList
     IMGUI_API ImU32         GetColorU32(const ImVec4& col);                                 // retrieve given color with style alpha applied, packed as a 32-bit value suitable for ImDrawList
-    IMGUI_API ImU32         GetColorU32(ImU32 col);                                         // retrieve given color with style alpha applied, packed as a 32-bit value suitable for ImDrawList
+    IMGUI_API ImU32         GetColorU32(ImU32 col, float alpha_mul = 1.0f);                 // retrieve given color with style alpha applied, packed as a 32-bit value suitable for ImDrawList
     IMGUI_API const ImVec4& GetStyleColorVec4(ImGuiCol idx);                                // retrieve style color as stored in ImGuiStyle structure. use to feed back into PushStyleColor(), otherwise use GetColorU32() to get style color with style alpha baked in.
 
     // Layout cursor positioning

imgui_internal.h

@@ -2481,6 +2481,7 @@ struct IMGUI_API ImGuiWindowTempData
     int                     CurrentTableIdx;        // Current table index (into g.Tables)
     ImGuiLayoutType         LayoutType;
     ImGuiLayoutType         ParentLayoutType;       // Layout type of parent window at the time of Begin()
+    ImU32                   ModalDimBgColor;
 
     // Local parameters stacks
     // We store the current settings outside of the vectors to increase memory locality (reduce cache misses). The vectors are rarely modified. Also it allows us to not heap allocate for short-lived windows which are not using those settings.