Disabled: Fixed an issue restoring Alpha in EndDisabled() when using nested BeginDisabled() calls with PushStyleVar(ImGuiStyleVar_DisabledAlpha) within. (#8454, #7640)

docs/CHANGELOG.txt

@@ -103,6 +103,8 @@ Other changes:
   (#8451, #7660) [@achabense]
 - TextLinkOpenURL(): fixed default Win32 io.PlatformOpenInShellFn handler to
   handle UTF-8 regardless of system regional settings. (#7660) [@achabense]
+- Disabled: Fixed an issue restoring Alpha in EndDisabled() when using nested
+  BeginDisabled() calls with PushStyleVar(ImGuiStyleVar_DisabledAlpha) within. (#8454, #7640)
 - Clipper: Fixed an issue where passing an out of bound index to IncludeItemByIndex()
   could incorrectly offset the final cursor, even if that index was not iterated through.
   One case where it would manifest was calling Combo() with an out of range index. (#8450)

imgui.cpp

@@ -7084,6 +7084,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     window_stack_data.Window = window;
     window_stack_data.ParentLastItemDataBackup = g.LastItemData;
     window_stack_data.DisabledOverrideReenable = (flags & ImGuiWindowFlags_Tooltip) && (g.CurrentItemFlags & ImGuiItemFlags_Disabled);
+    window_stack_data.DisabledOverrideReenableAlphaBackup = 0.0f;
     ErrorRecoveryStoreState(&window_stack_data.StackSizesInBegin);
     g.StackSizesInBeginForCurrentWindow = &window_stack_data.StackSizesInBegin;
     if (flags & ImGuiWindowFlags_ChildMenu)
@@ -7950,6 +7951,7 @@ void ImGui::BeginDisabledOverrideReenable()
 {
     ImGuiContext& g = *GImGui;
     IM_ASSERT(g.CurrentItemFlags & ImGuiItemFlags_Disabled);
+    g.CurrentWindowStack.back().DisabledOverrideReenableAlphaBackup = g.Style.Alpha;
     g.Style.Alpha = g.DisabledAlphaBackup;
     g.CurrentItemFlags &= ~ImGuiItemFlags_Disabled;
     g.ItemFlagsStack.push_back(g.CurrentItemFlags);
@@ -7963,7 +7965,7 @@ void ImGui::EndDisabledOverrideReenable()
     IM_ASSERT(g.DisabledStackSize > 0);
     g.ItemFlagsStack.pop_back();
     g.CurrentItemFlags = g.ItemFlagsStack.back();
-    g.Style.Alpha = g.DisabledAlphaBackup * g.Style.DisabledAlpha;
+    g.Style.Alpha = g.CurrentWindowStack.back().DisabledOverrideReenableAlphaBackup;
 }
 
 void ImGui::PushTextWrapPos(float wrap_pos_x)

imgui_internal.h

@@ -1316,6 +1316,7 @@ struct ImGuiWindowStackData
     ImGuiLastItemData       ParentLastItemDataBackup;
     ImGuiErrorRecoveryState StackSizesInBegin;          // Store size of various stacks for asserting
     bool                    DisabledOverrideReenable;   // Non-child window override disabled flag
+    float                   DisabledOverrideReenableAlphaBackup;
 };
 
 struct ImGuiShrinkWidthItem