ColorEdit, ColorPicker: (Breaking) redesigned how alpha is displayed in the preview square. (#8335, #1578, #346)

Added ImGuiColorEditFlags_AlphaOpaque, ImGuiColorEditFlags_AlphaNoBg.
Removed ImGuiColorEditFlags_AlphaPreview.

docs/CHANGELOG.txt

@@ -41,6 +41,14 @@ HOW TO UPDATE?
 
 Breaking changes:
 
+- ColorEdit, ColorPicker: redesigned how alpha is displayed in the preview square. (#8335, #1578, #346)
+   - Removed ImGuiColorEditFlags_AlphaPreview (made value 0): it is now the default behavior.
+   - Prior to 1.91.8: alpha was made opaque in the preview by default _unless_ using ImGuiColorEditFlags_AlphaPreview.
+   - We now display the preview as transparent by default. You can use ImGuiColorEditFlags_AlphaOpaque to use old behavior.
+   - The new flags may be combined better and allow finer controls:
+     - ImGuiColorEditFlags_AlphaOpaque: disable alpha in the preview, but alpha value still editable.
+     - ImGuiColorEditFlags_AlphaNoBg: disable rendering a checkerboard background behind transparent color.
+     - ImGuiColorEditFlags_AlphaPreviewHalf: display half opaque / half transparent preview.
 - Backends: SDLGPU3: Renamed ImGui_ImplSDLGPU3_InitInfo::GpuDevice to Device
   for consistency. (#8163, #7998, #7988)
 

imgui.cpp

@@ -430,6 +430,9 @@ CODE
  When you are not sure about an old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
  You can read releases logs https://github.com/ocornut/imgui/releases for more details.
 
+ - 2025/01/22 (1.91.8) - removed ImGuiColorEditFlags_AlphaPreview (made value 0): it is now the default behavior.
+                         prior to 1.91.8: alpha was made opaque in the preview by default _unless_ using ImGuiColorEditFlags_AlphaPreview. We now display the preview as transparent by default. You can use ImGuiColorEditFlags_AlphaOpaque to use old behavior.
+                         the new flags (ImGuiColorEditFlags_AlphaOpaque, ImGuiColorEditFlags_AlphaNoBg + existing ImGuiColorEditFlags_AlphaPreviewHalf) may be combined better and allow finer controls:
  - 2025/01/14 (1.91.7) - renamed ImGuiTreeNodeFlags_SpanTextWidth to ImGuiTreeNodeFlags_SpanLabelWidth for consistency with other names. Kept redirection enum (will obsolete). (#6937)
  - 2024/11/27 (1.91.6) - changed CRC32 table from CRC32-adler to CRC32c polynomial in order to be compatible with the result of SSE 4.2 instructions.
                          As a result, old .ini data may be partially lost (docking and tables information particularly).

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   19172
+#define IMGUI_VERSION_NUM   19173
 #define IMGUI_HAS_TABLE
 
 /*
@@ -1753,8 +1753,14 @@ enum ImGuiColorEditFlags_
     ImGuiColorEditFlags_NoSidePreview   = 1 << 8,   //              // ColorPicker: disable bigger color preview on right side of the picker, use small color square preview instead.
     ImGuiColorEditFlags_NoDragDrop      = 1 << 9,   //              // ColorEdit: disable drag and drop target. ColorButton: disable drag and drop source.
     ImGuiColorEditFlags_NoBorder        = 1 << 10,  //              // ColorButton: disable border (which is enforced by default)
-    ImGuiColorEditFlags_AlphaPreview    = 1 << 11,  //              // ColorEdit, ColorPicker, ColorButton: display preview as a transparent color over a checkerboard, instead of opaque.
-    ImGuiColorEditFlags_AlphaPreviewHalf= 1 << 12,  //              // ColorEdit, ColorPicker, ColorButton: display half opaque / half checkerboard, instead of opaque.
+
+    // Alpha preview
+    // - Prior to 1.91.8 (2025/01/21): alpha was made opaque in the preview by default using old name ImGuiColorEditFlags_AlphaPreview.
+    // - We now display the preview as transparent by default. You can use ImGuiColorEditFlags_AlphaOpaque to use old behavior.
+    // - The new flags may be combined better and allow finer controls.
+    ImGuiColorEditFlags_AlphaOpaque     = 1 << 11,  //              // ColorEdit, ColorPicker, ColorButton: disable alpha in the preview,. Contrary to _NoAlpha it may still be edited when calling ColorEdit4()/ColorPicker4(). For ColorButton() this does the same as _NoAlpha.
+    ImGuiColorEditFlags_AlphaNoBg       = 1 << 12,  //              // ColorEdit, ColorPicker, ColorButton: disable rendering a checkerboard background behind transparent color.
+    ImGuiColorEditFlags_AlphaPreviewHalf= 1 << 13,  //              // ColorEdit, ColorPicker, ColorButton: display half opaque / half transparent preview.
 
     // User Options (right-click on widget to change some of them).
     ImGuiColorEditFlags_AlphaBar        = 1 << 16,  //              // ColorEdit, ColorPicker: show vertical alpha bar/gradient in picker.
@@ -1774,12 +1780,16 @@ enum ImGuiColorEditFlags_
     ImGuiColorEditFlags_DefaultOptions_ = ImGuiColorEditFlags_Uint8 | ImGuiColorEditFlags_DisplayRGB | ImGuiColorEditFlags_InputRGB | ImGuiColorEditFlags_PickerHueBar,
 
     // [Internal] Masks
+    ImGuiColorEditFlags_AlphaMask_      = ImGuiColorEditFlags_NoAlpha | ImGuiColorEditFlags_AlphaOpaque | ImGuiColorEditFlags_AlphaNoBg | ImGuiColorEditFlags_AlphaPreviewHalf,
     ImGuiColorEditFlags_DisplayMask_    = ImGuiColorEditFlags_DisplayRGB | ImGuiColorEditFlags_DisplayHSV | ImGuiColorEditFlags_DisplayHex,
     ImGuiColorEditFlags_DataTypeMask_   = ImGuiColorEditFlags_Uint8 | ImGuiColorEditFlags_Float,
     ImGuiColorEditFlags_PickerMask_     = ImGuiColorEditFlags_PickerHueWheel | ImGuiColorEditFlags_PickerHueBar,
     ImGuiColorEditFlags_InputMask_      = ImGuiColorEditFlags_InputRGB | ImGuiColorEditFlags_InputHSV,
 
     // Obsolete names
+#ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+    ImGuiColorEditFlags_AlphaPreview = 0,         // [Removed in 1.91.8] This is the default now. Will display a checkerboard unless ImGuiColorEditFlags_AlphaNoBg is set.
+#endif
     //ImGuiColorEditFlags_RGB = ImGuiColorEditFlags_DisplayRGB, ImGuiColorEditFlags_HSV = ImGuiColorEditFlags_DisplayHSV, ImGuiColorEditFlags_HEX = ImGuiColorEditFlags_DisplayHex  // [renamed in 1.69]
 };
 

imgui_demo.cpp

@@ -2117,11 +2117,12 @@ static void ShowDemoWindowWidgets(ImGuiDemoWindowData* demo_data)
     if (ImGui::TreeNode("Color/Picker Widgets"))
     {
         static ImVec4 color = ImVec4(114.0f / 255.0f, 144.0f / 255.0f, 154.0f / 255.0f, 200.0f / 255.0f);
-        static ImGuiColorEditFlags base_flags = ImGuiColorEditFlags_AlphaPreview;
+        static ImGuiColorEditFlags base_flags = ImGuiColorEditFlags_None;
 
         ImGui::SeparatorText("Options");
         ImGui::CheckboxFlags("ImGuiColorEditFlags_NoAlpha", &base_flags, ImGuiColorEditFlags_NoAlpha);
-        ImGui::CheckboxFlags("ImGuiColorEditFlags_AlphaPreview", &base_flags, ImGuiColorEditFlags_AlphaPreview);
+        ImGui::CheckboxFlags("ImGuiColorEditFlags_AlphaOpaque", &base_flags, ImGuiColorEditFlags_AlphaOpaque);
+        ImGui::CheckboxFlags("ImGuiColorEditFlags_AlphaNoBg", &base_flags, ImGuiColorEditFlags_AlphaNoBg);
         ImGui::CheckboxFlags("ImGuiColorEditFlags_AlphaPreviewHalf", &base_flags, ImGuiColorEditFlags_AlphaPreviewHalf);
         ImGui::CheckboxFlags("ImGuiColorEditFlags_NoDragDrop", &base_flags, ImGuiColorEditFlags_NoDragDrop);
         ImGui::CheckboxFlags("ImGuiColorEditFlags_NoOptions", &base_flags, ImGuiColorEditFlags_NoOptions); ImGui::SameLine(); HelpMarker("Right-click on the individual color widget to show options.");
@@ -8047,9 +8048,9 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
             filter.Draw("Filter colors", ImGui::GetFontSize() * 16);
 
             static ImGuiColorEditFlags alpha_flags = 0;
-            if (ImGui::RadioButton("Opaque", alpha_flags == ImGuiColorEditFlags_None))             { alpha_flags = ImGuiColorEditFlags_None; } ImGui::SameLine();
-            if (ImGui::RadioButton("Alpha",  alpha_flags == ImGuiColorEditFlags_AlphaPreview))     { alpha_flags = ImGuiColorEditFlags_AlphaPreview; } ImGui::SameLine();
-            if (ImGui::RadioButton("Both",   alpha_flags == ImGuiColorEditFlags_AlphaPreviewHalf)) { alpha_flags = ImGuiColorEditFlags_AlphaPreviewHalf; } ImGui::SameLine();
+            if (ImGui::RadioButton("Opaque", alpha_flags == ImGuiColorEditFlags_AlphaOpaque))       { alpha_flags = ImGuiColorEditFlags_AlphaOpaque; } ImGui::SameLine();
+            if (ImGui::RadioButton("Alpha",  alpha_flags == ImGuiColorEditFlags_None))              { alpha_flags = ImGuiColorEditFlags_None; } ImGui::SameLine();
+            if (ImGui::RadioButton("Both",   alpha_flags == ImGuiColorEditFlags_AlphaPreviewHalf))  { alpha_flags = ImGuiColorEditFlags_AlphaPreviewHalf; } ImGui::SameLine();
             HelpMarker(
                 "In the color list:\n"
                 "Left-click on color square to open color picker,\n"

imgui_widgets.cpp

@@ -5902,7 +5902,7 @@ bool ImGui::ColorPicker4(const char* label, float col[4], ImGuiColorEditFlags fl
         if ((flags & ImGuiColorEditFlags_NoLabel))
             Text("Current");
 
-        ImGuiColorEditFlags sub_flags_to_forward = ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_HDR | ImGuiColorEditFlags_AlphaPreview | ImGuiColorEditFlags_AlphaPreviewHalf | ImGuiColorEditFlags_NoTooltip;
+        ImGuiColorEditFlags sub_flags_to_forward = ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_HDR | ImGuiColorEditFlags_AlphaMask_ | ImGuiColorEditFlags_NoTooltip;
         ColorButton("##current", col_v4, (flags & sub_flags_to_forward), ImVec2(square_sz * 3, square_sz * 2));
         if (ref_col != NULL)
         {
@@ -5942,7 +5942,7 @@ bool ImGui::ColorPicker4(const char* label, float col[4], ImGuiColorEditFlags fl
     if ((flags & ImGuiColorEditFlags_NoInputs) == 0)
     {
         PushItemWidth((alpha_bar ? bar1_pos_x : bar0_pos_x) + bars_width - picker_pos.x);
-        ImGuiColorEditFlags sub_flags_to_forward = ImGuiColorEditFlags_DataTypeMask_ | ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_HDR | ImGuiColorEditFlags_NoAlpha | ImGuiColorEditFlags_NoOptions | ImGuiColorEditFlags_NoTooltip | ImGuiColorEditFlags_NoSmallPreview | ImGuiColorEditFlags_AlphaPreview | ImGuiColorEditFlags_AlphaPreviewHalf;
+        ImGuiColorEditFlags sub_flags_to_forward = ImGuiColorEditFlags_DataTypeMask_ | ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_HDR | ImGuiColorEditFlags_AlphaMask_ | ImGuiColorEditFlags_NoOptions | ImGuiColorEditFlags_NoTooltip | ImGuiColorEditFlags_NoSmallPreview;
         ImGuiColorEditFlags sub_flags = (flags & sub_flags_to_forward) | ImGuiColorEditFlags_NoPicker;
         if (flags & ImGuiColorEditFlags_DisplayRGB || (flags & ImGuiColorEditFlags_DisplayMask_) == 0)
             if (ColorEdit4("##rgb", col, sub_flags | ImGuiColorEditFlags_DisplayRGB))
@@ -6118,8 +6118,8 @@ bool ImGui::ColorButton(const char* desc_id, const ImVec4& col, ImGuiColorEditFl
     bool hovered, held;
     bool pressed = ButtonBehavior(bb, id, &hovered, &held);
 
-    if (flags & ImGuiColorEditFlags_NoAlpha)
-        flags &= ~(ImGuiColorEditFlags_AlphaPreview | ImGuiColorEditFlags_AlphaPreviewHalf);
+    if (flags & (ImGuiColorEditFlags_NoAlpha | ImGuiColorEditFlags_AlphaOpaque))
+        flags &= ~(ImGuiColorEditFlags_AlphaNoBg | ImGuiColorEditFlags_AlphaPreviewHalf);
 
     ImVec4 col_rgb = col;
     if (flags & ImGuiColorEditFlags_InputHSV)
@@ -6138,14 +6138,17 @@ bool ImGui::ColorButton(const char* desc_id, const ImVec4& col, ImGuiColorEditFl
     if ((flags & ImGuiColorEditFlags_AlphaPreviewHalf) && col_rgb.w < 1.0f)
     {
         float mid_x = IM_ROUND((bb_inner.Min.x + bb_inner.Max.x) * 0.5f);
-        RenderColorRectWithAlphaCheckerboard(window->DrawList, ImVec2(bb_inner.Min.x + grid_step, bb_inner.Min.y), bb_inner.Max, GetColorU32(col_rgb), grid_step, ImVec2(-grid_step + off, off), rounding, ImDrawFlags_RoundCornersRight);
+        if ((flags & ImGuiColorEditFlags_AlphaNoBg) == 0)
+            RenderColorRectWithAlphaCheckerboard(window->DrawList, ImVec2(bb_inner.Min.x + grid_step, bb_inner.Min.y), bb_inner.Max, GetColorU32(col_rgb), grid_step, ImVec2(-grid_step + off, off), rounding, ImDrawFlags_RoundCornersRight);
+        else
+            window->DrawList->AddRectFilled(ImVec2(bb_inner.Min.x + grid_step, bb_inner.Min.y), bb_inner.Max, GetColorU32(col_rgb), rounding, ImDrawFlags_RoundCornersRight);
         window->DrawList->AddRectFilled(bb_inner.Min, ImVec2(mid_x, bb_inner.Max.y), GetColorU32(col_rgb_without_alpha), rounding, ImDrawFlags_RoundCornersLeft);
     }
     else
     {
         // Because GetColorU32() multiplies by the global style Alpha and we don't want to display a checkerboard if the source code had no alpha
-        ImVec4 col_source = (flags & ImGuiColorEditFlags_AlphaPreview) ? col_rgb : col_rgb_without_alpha;
-        if (col_source.w < 1.0f)
+        ImVec4 col_source = (flags & ImGuiColorEditFlags_AlphaOpaque) ? col_rgb_without_alpha : col_rgb;
+        if (col_source.w < 1.0f && (flags & ImGuiColorEditFlags_AlphaNoBg) == 0)
             RenderColorRectWithAlphaCheckerboard(window->DrawList, bb_inner.Min, bb_inner.Max, GetColorU32(col_source), grid_step, ImVec2(off, off), rounding);
         else
             window->DrawList->AddRectFilled(bb_inner.Min, bb_inner.Max, GetColorU32(col_source), rounding);
@@ -6175,7 +6178,7 @@ bool ImGui::ColorButton(const char* desc_id, const ImVec4& col, ImGuiColorEditFl
 
     // Tooltip
     if (!(flags & ImGuiColorEditFlags_NoTooltip) && hovered && IsItemHovered(ImGuiHoveredFlags_ForTooltip))
-        ColorTooltip(desc_id, &col.x, flags & (ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_NoAlpha | ImGuiColorEditFlags_AlphaPreview | ImGuiColorEditFlags_AlphaPreviewHalf));
+        ColorTooltip(desc_id, &col.x, flags & (ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_AlphaMask_));
 
     return pressed;
 }
@@ -6216,7 +6219,8 @@ void ImGui::ColorTooltip(const char* text, const float* col, ImGuiColorEditFlags
     ImVec2 sz(g.FontSize * 3 + g.Style.FramePadding.y * 2, g.FontSize * 3 + g.Style.FramePadding.y * 2);
     ImVec4 cf(col[0], col[1], col[2], (flags & ImGuiColorEditFlags_NoAlpha) ? 1.0f : col[3]);
     int cr = IM_F32_TO_INT8_SAT(col[0]), cg = IM_F32_TO_INT8_SAT(col[1]), cb = IM_F32_TO_INT8_SAT(col[2]), ca = (flags & ImGuiColorEditFlags_NoAlpha) ? 255 : IM_F32_TO_INT8_SAT(col[3]);
-    ColorButton("##preview", cf, (flags & (ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_NoAlpha | ImGuiColorEditFlags_AlphaPreview | ImGuiColorEditFlags_AlphaPreviewHalf)) | ImGuiColorEditFlags_NoTooltip, sz);
+    ImGuiColorEditFlags flags_to_forward = ImGuiColorEditFlags_InputMask_ | ImGuiColorEditFlags_AlphaMask_;
+    ColorButton("##preview", cf, (flags & flags_to_forward) | ImGuiColorEditFlags_NoTooltip, sz);
     SameLine();
     if ((flags & ImGuiColorEditFlags_InputRGB) || !(flags & ImGuiColorEditFlags_InputMask_))
     {