Shadows: WIP for latest (refreshing UV coordinates).

(merged 10 commits, removing dynamic tex config, moved tex config to internal structs, removed back-end changes)
(squashed 2025-06-11, fixed conflict, doesn't build as-is)
Shadows: Added IMGUI_HAS_SHADOWS
Shadows: Demo code in Custom Rendering section. Added AddShadowRectFilled() variant. BeginMainMenuBar() disable shadows.
Shadows: Added initial version of convex shape shadow code.
(+stripped out of original polygon generation demo, moved to imgui_dev)
Shadows: Tweak demo to use AddShadowCircle() functions + fix warnings.
 (+ stripped old polygon generation code from commits)
Shadows: Convex shape shadow improvement/fixes
- Fixed pixel cracking on convex shadow edges
- Added convex shadow offset support
- Fixed some convex shadow fringing issues
- Added convex shadow demo code
Shadows: Added ImDrawShadowFlags, simplified API surface, reordered parameters
+ fix minor warnings
+ removed NGon variant for now.
Shadows: Re-added AddShadowNGon().
Shadows: Shallow styling tweaks and renaming for consistency.
Shadows: Fixes + two fixes for PVS Studio static analyzer.
Shadows: Fix for latest, reuse ImDrawList, remove ImDrawShadowFlags.
Shadows: Fix to support for colored-only font atlas. (4202)
Shadows: Fix broken shadows due to zero-clear added in 9417acc2.
Shadows: remove use of GetWindowContentRegionMax().

imgui.cpp

@@ -1323,6 +1323,7 @@ static void             UpdateTexturesNewFrame();
 static void             UpdateTexturesEndFrame();
 static void             UpdateSettings();
 static int              UpdateWindowManualResize(ImGuiWindow* window, const ImVec2& size_auto_fit, int* border_hovered, int* border_held, int resize_grip_count, ImU32 resize_grip_col[4], const ImRect& visibility_rect);
+static void             RenderWindowShadow(ImGuiWindow* window);
 static void             RenderWindowOuterBorders(ImGuiWindow* window);
 static void             RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, bool handle_borders_and_resize_grips, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size);
 static void             RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open);
@@ -1444,6 +1445,9 @@ ImGuiStyle::ImGuiStyle()
     AntiAliasedFill             = true;             // Enable anti-aliased filled shapes (rounded rectangles, circles, etc.).
     CurveTessellationTol        = 1.25f;            // Tessellation tolerance when using PathBezierCurveTo() without a specific number of segments. Decrease for highly tessellated curves (higher quality, more polygons), increase to reduce quality.
     CircleTessellationMaxError  = 0.30f;            // Maximum error (in pixels) allowed when using AddCircle()/AddCircleFilled() or drawing rounded corner rectangles with no explicit segment count specified. Decrease for higher quality but more geometry.
+    WindowShadowSize            = 100.0f;           // Size (in pixels) of window shadows.
+    WindowShadowOffsetDist      = 0.0f;             // Offset distance (in pixels) of window shadows from casting window.
+    WindowShadowOffsetAngle     = IM_PI * 0.25f;    // Offset angle of window shadows from casting window (0.0f = left, 0.5f*PI = bottom, 1.0f*PI = right, 1.5f*PI = top).
 
     // Behaviors
     HoverStationaryDelay        = 0.15f;            // Delay for IsItemHovered(ImGuiHoveredFlags_Stationary). Time required to consider mouse stationary.
@@ -3670,6 +3674,7 @@ const char* ImGui::GetStyleColorName(ImGuiCol idx)
     case ImGuiCol_NavWindowingHighlight: return "NavWindowingHighlight";
     case ImGuiCol_NavWindowingDimBg: return "NavWindowingDimBg";
     case ImGuiCol_ModalWindowDimBg: return "ModalWindowDimBg";
+    case ImGuiCol_WindowShadow: return "WindowShadow";
     }
     IM_ASSERT(0);
     return "Unknown";
@@ -7004,6 +7009,11 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
             window->DrawList->AddRectFilled(window->Pos + ImVec2(0, window->TitleBarHeight), window->Pos + window->Size, bg_col, window_rounding, (flags & ImGuiWindowFlags_NoTitleBar) ? 0 : ImDrawFlags_RoundCornersBottom);
         }
 
+        // Draw window shadow
+        if (style.WindowShadowSize > 0.0f && (!(flags & ImGuiWindowFlags_ChildWindow) || (flags & ImGuiWindowFlags_Popup)))
+            if (style.Colors[ImGuiCol_WindowShadow].w > 0.0f)
+                RenderWindowShadow(window);
+
         // Title bar
         if (!(flags & ImGuiWindowFlags_NoTitleBar))
         {
@@ -7052,6 +7062,16 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
     window->DC.NavLayerCurrent = ImGuiNavLayer_Main;
 }
 
+void ImGui::RenderWindowShadow(ImGuiWindow* window)
+{
+    ImGuiContext& g = *GImGui;
+    ImGuiStyle& style = g.Style;
+    float shadow_size = style.WindowShadowSize;
+    ImU32 shadow_col = GetColorU32(ImGuiCol_WindowShadow);
+    ImVec2 shadow_offset = ImVec2(ImCos(style.WindowShadowOffsetAngle), ImSin(style.WindowShadowOffsetAngle)) * style.WindowShadowOffsetDist;
+    window->DrawList->AddShadowRect(window->Pos, window->Pos + window->Size, shadow_col, shadow_size, shadow_offset, ImDrawFlags_ShadowCutOutShapeBackground, window->WindowRounding);
+}
+
 // Render title text, collapse button, close button
 void ImGui::RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open)
 {
@@ -8896,6 +8916,12 @@ void ImGui::UpdateCurrentFontSize(float restore_font_size_after_scaling)
     g.FontBakedScale = (g.Font != NULL && window != NULL) ? (g.FontSize / g.FontBaked->Size) : 0.0f;
     g.DrawListSharedData.FontSize = g.FontSize;
     g.DrawListSharedData.FontScale = g.FontBakedScale;
+    if (g.Font)
+    {
+        ImFontAtlas* atlas = g.Font->ContainerAtlas;
+        g.DrawListSharedData.ShadowRectIds = &atlas->ShadowRectIds[0];
+        g.DrawListSharedData.ShadowRectUvs = &atlas->ShadowRectUvs[0];
+    }
 }
 
 // Exposed in case user may want to override setting density.

imgui.h

@@ -1764,6 +1764,7 @@ enum ImGuiCol_
     ImGuiCol_NavWindowingHighlight, // Highlight window when using CTRL+TAB
     ImGuiCol_NavWindowingDimBg,     // Darken/colorize entire screen behind the CTRL+TAB window list, when active
     ImGuiCol_ModalWindowDimBg,      // Darken/colorize entire screen behind a modal window, when one is active
+    ImGuiCol_WindowShadow,          // Window shadows
     ImGuiCol_COUNT,
 
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
@@ -2303,6 +2304,10 @@ struct ImGuiStyle
     float       CurveTessellationTol;       // Tessellation tolerance when using PathBezierCurveTo() without a specific number of segments. Decrease for highly tessellated curves (higher quality, more polygons), increase to reduce quality.
     float       CircleTessellationMaxError; // Maximum error (in pixels) allowed when using AddCircle()/AddCircleFilled() or drawing rounded corner rectangles with no explicit segment count specified. Decrease for higher quality but more geometry.
 
+    float       WindowShadowSize;           // Size (in pixels) of window shadows. Set this to zero to disable shadows.
+    float       WindowShadowOffsetDist;     // Offset distance (in pixels) of window shadows from casting window.
+    float       WindowShadowOffsetAngle;    // Offset angle of window shadows from casting window (0.0f = left, 0.5f*PI = bottom, 1.0f*PI = right, 1.5f*PI = top).
+
     // Colors
     ImVec4      Colors[ImGuiCol_COUNT];
 
@@ -3189,6 +3194,7 @@ enum ImDrawFlags_
     ImDrawFlags_RoundCornersAll             = ImDrawFlags_RoundCornersTopLeft | ImDrawFlags_RoundCornersTopRight | ImDrawFlags_RoundCornersBottomLeft | ImDrawFlags_RoundCornersBottomRight,
     ImDrawFlags_RoundCornersDefault_        = ImDrawFlags_RoundCornersAll, // Default to ALL corners if none of the _RoundCornersXX flags are specified.
     ImDrawFlags_RoundCornersMask_           = ImDrawFlags_RoundCornersAll | ImDrawFlags_RoundCornersNone,
+    ImDrawFlags_ShadowCutOutShapeBackground = 1 << 9, // Do not render the shadow shape under the objects to be shadowed to save on fill-rate or facilitate blending. Slower on CPU.
 };
 
 // Flags for ImDrawList instance. Those are set automatically by ImGui:: functions from ImGuiIO settings, and generally not manipulated directly.
@@ -3287,6 +3293,23 @@ struct ImDrawList
     IMGUI_API void  AddImageQuad(ImTextureRef tex_ref, const ImVec2& p1, const ImVec2& p2, const ImVec2& p3, const ImVec2& p4, const ImVec2& uv1 = ImVec2(0, 0), const ImVec2& uv2 = ImVec2(1, 0), const ImVec2& uv3 = ImVec2(1, 1), const ImVec2& uv4 = ImVec2(0, 1), ImU32 col = IM_COL32_WHITE);
     IMGUI_API void  AddImageRounded(ImTextureRef tex_ref, const ImVec2& p_min, const ImVec2& p_max, const ImVec2& uv_min, const ImVec2& uv_max, ImU32 col, float rounding, ImDrawFlags flags = 0);
 
+    // Shadows primitives
+    // [BETA] API
+    // - Add shadow for a object, with min/max or center/radius describing the object extents, and offset shifting the shadow.
+    // - Rounding parameters refer to the object itself, not the shadow!
+    // - By default, the area under the object is filled, because this is simpler to process.
+    //   Using the ImDrawFlags_ShadowCutOutShapeBackground flag makes the function not render this area and leave a hole under the object.
+    //    - Shadows w/ fill under the object: a bit faster for CPU, more pixels rendered, visible/darkening if used behind a transparent shape.
+    //      Typically used by: small, frequent objects, opaque objects, transparent objects if shadow darkening isn't an issue.
+    //    - Shadows w/ hole under the object: a bit slower for CPU, less pixels rendered, no difference if used behind a transparent shape.
+    //      Typically used by: large, infrequent objects, transparent objects if exact blending/color matter.
+    // - FIXME-SHADOWS: 'offset' + ImDrawFlags_ShadowCutOutShapeBackground are not currently supported together with AddShadowCircle(), AddShadowConvexPoly(), AddShadowNGon().
+    #define IMGUI_HAS_SHADOWS 1
+    IMGUI_API void  AddShadowRect(const ImVec2& obj_min, const ImVec2& obj_max, ImU32 shadow_col, float shadow_thickness, const ImVec2& shadow_offset, ImDrawFlags flags = 0, float obj_rounding = 0.0f);
+    IMGUI_API void  AddShadowCircle(const ImVec2& obj_center, float obj_radius, ImU32 shadow_col, float shadow_thickness, const ImVec2& shadow_offset, ImDrawFlags flags = 0, int obj_num_segments = 12);
+    IMGUI_API void  AddShadowConvexPoly(const ImVec2* points, int points_count, ImU32 shadow_col, float shadow_thickness, const ImVec2& shadow_offset, ImDrawFlags flags = 0);
+    IMGUI_API void  AddShadowNGon(const ImVec2& obj_center, float obj_radius, ImU32 shadow_col, float shadow_thickness, const ImVec2& shadow_offset, ImDrawFlags flags, int obj_num_segments);
+
     // Stateful path API, add points then finish with PathFillConvex() or PathStroke()
     // - Important: filled shapes must always use clockwise winding order! The anti-aliasing fringe depends on it. Counter-clockwise shapes will have "inward" anti-aliasing.
     //   so e.g. 'PathArcTo(center, radius, PI * -0.5f, PI)' is ok, whereas 'PathArcTo(center, radius, PI, PI * -0.5f)' won't have correct anti-aliasing when followed by PathFillConvex().
@@ -3475,6 +3498,24 @@ struct ImTextureData
 // [SECTION] Font API (ImFontConfig, ImFontGlyph, ImFontAtlasFlags, ImFontAtlas, ImFontGlyphRangesBuilder, ImFont)
 //-----------------------------------------------------------------------------
 
+// [Internal] Shadow texture baking config
+struct ImFontAtlasShadowTexConfig
+{
+    int     TexCornerSize;          // Size of the corner areas.
+    int     TexEdgeSize;            // Size of the edge areas (and by extension the center). Changing this is normally unnecessary.
+    float   TexFalloffPower;        // The power factor for the shadow falloff curve.
+    float   TexDistanceFieldOffset; // How much to offset the distance field by (allows over/under-shadowing, potentially useful for accommodating rounded corners on the "casting" shape).
+    bool    TexBlur;                // Do we want to Gaussian blur the shadow texture?
+
+    inline ImFontAtlasShadowTexConfig() { memset(this, 0, sizeof(*this)); }
+    IMGUI_API void SetupDefaults();
+    int     GetRectTexPadding() const   { return 2; }                                                   // Number of pixels of padding to add to the rectangular texture to avoid sampling artifacts at the edges.
+    int     CalcRectTexSize() const     { return TexCornerSize + TexEdgeSize + GetRectTexPadding(); }   // The size of the texture area required for the actual 2x2 rectangle shadow texture (after the redundant corners have been removed). Padding is required here to avoid sampling artifacts at the edge adjoining the removed corners.    int     CalcConvexTexWidth() const;                                                                // The width of the texture area required for the convex shape shadow texture.
+    int     GetConvexTexPadding() const { return 8; }                                                   // Number of pixels of padding to add to the convex shape texture to avoid sampling artifacts at the edges. This also acts as padding for the expanded corner triangles.
+    int     CalcConvexTexWidth() const;                                                                 // The width of the texture area required for the convex shape shadow texture.
+    int     CalcConvexTexHeight() const;                                                                // The height of the texture area required for the convex shape shadow texture.
+};
+
 // A font input/source (we may rename this to ImFontSource in the future)
 struct ImFontConfig
 {
@@ -3721,6 +3762,11 @@ struct ImFontAtlas
     int                         RefCount;           // Number of contexts using this atlas
     ImGuiContext*               OwnerContext;       // Context which own the atlas will be in charge of updating and destroying it.
 
+    // [Internal] Shadow data
+    ImFontAtlasRectId           ShadowRectIds[2];   // IDs of rect for shadow textures
+    ImVec4                      ShadowRectUvs[10];  // UV coordinates for shadow textures, 9 for the rectangle shadows and the final entry for the convex shape shadows
+    ImFontAtlasShadowTexConfig  ShadowTexConfig;    // Shadow texture baking config
+
     // [Obsolete]
 #ifndef IMGUI_DISABLE_OBSOLETE_FUNCTIONS
     // Legacy: You can request your rectangles to be mapped as font glyph (given a font + Unicode point), so you can render e.g. custom colorful icons and use them as regular glyphs. --> Prefer using a custom ImFontLoader.

imgui_demo.cpp

@@ -8576,6 +8576,22 @@ void ImGui::ShowStyleEditor(ImGuiStyle* ref)
             EndTabItem();
         }
 
+        if (BeginTabItem("Shadows"))
+        {
+            Text("Window shadows:");
+            ColorEdit4("Color", (float*)&style.Colors[ImGuiCol_WindowShadow], ImGuiColorEditFlags_AlphaBar);
+            SameLine();
+            HelpMarker("Same as 'WindowShadow' in Colors tab.");
+
+            SliderFloat("Size", &style.WindowShadowSize, 0.0f, 128.0f, "%.1f");
+            SameLine();
+            HelpMarker("Set shadow size to zero to disable shadows.");
+            SliderFloat("Offset distance", &style.WindowShadowOffsetDist, 0.0f, 64.0f, "%.0f");
+            SliderAngle("Offset angle", &style.WindowShadowOffsetAngle);
+
+            EndTabItem();
+        }
+
         EndTabBar();
     }
     PopItemWidth();
@@ -10047,6 +10063,168 @@ static void ShowExampleAppCustomRendering(bool* p_open)
             ImGui::EndTabItem();
         }
 
+        if (ImGui::BeginTabItem("Shadows"))
+        {
+            static float shadow_thickness = 40.0f;
+            static ImVec4 shadow_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
+            static bool shadow_filled = false;
+            static ImVec4 shape_color = ImVec4(0.9f, 0.6f, 0.3f, 1.0f);
+            static float shape_rounding = 0.0f;
+            static ImVec2 shadow_offset(0.0f, 0.0f);
+            static ImVec4 background_color = ImVec4(0.5f, 0.5f, 0.7f, 1.0f);
+            static bool wireframe = false;
+            static bool aa = true;
+            static int poly_shape_index = 0;
+            ImGui::Checkbox("Shadow filled", &shadow_filled);
+            ImGui::SameLine();
+            HelpMarker("This will fill the section behind the shape to shadow. It's often unnecessary and wasteful but provided for consistency.");
+            ImGui::Checkbox("Wireframe shapes", &wireframe);
+            ImGui::SameLine();
+            HelpMarker("This draws the shapes in wireframe so you can see the shadow underneath.");
+            ImGui::Checkbox("Anti-aliasing", &aa);
+
+            ImGui::DragFloat("Shadow Thickness", &shadow_thickness, 1.0f, 0.0f, 100.0f, "%.02f");
+            ImGui::SliderFloat2("Offset", (float*)&shadow_offset, -32.0f, 32.0f);
+            ImGui::SameLine();
+            HelpMarker("Note that currently circles/convex shapes do not support non-zero offsets for unfilled shadows.");
+            ImGui::ColorEdit4("Background Color", &background_color.x);
+            ImGui::ColorEdit4("Shadow Color", &shadow_color.x);
+            ImGui::ColorEdit4("Shape Color", &shape_color.x);
+            ImGui::DragFloat("Shape Rounding", &shape_rounding, 1.0f, 0.0f, 20.0f, "%.02f");
+            ImGui::Combo("Convex shape", &poly_shape_index, "Shape 1\0Shape 2\0Shape 3\0Shape 4\0Shape 4 (winding reversed)");
+
+            ImDrawList* draw_list = ImGui::GetWindowDrawList();
+            ImDrawListFlags old_flags = draw_list->Flags;
+
+            if (aa)
+                draw_list->Flags |= ~ImDrawListFlags_AntiAliasedFill;
+            else
+                draw_list->Flags &= ~ImDrawListFlags_AntiAliasedFill;
+
+            // Fill a strip of background
+            {
+                ImVec2 p = ImGui::GetCursorScreenPos();
+                draw_list->AddRectFilled(p, ImVec2(p.x + ImGui::GetContentRegionAvail().x, p.y + 200.0f), ImGui::GetColorU32(background_color));
+            }
+
+            // Rectangle
+            {
+                ImVec2 p = ImGui::GetCursorScreenPos();
+                ImGui::Dummy(ImVec2(200.0f, 200.0f));
+
+                ImVec2 r1(p.x + 50.0f, p.y + 50.0f);
+                ImVec2 r2(p.x + 150.0f, p.y + 150.0f);
+                ImDrawFlags draw_flags = shadow_filled ? ImDrawFlags_None : ImDrawFlags_ShadowCutOutShapeBackground;
+                draw_list->AddShadowRect(r1, r2, ImGui::GetColorU32(shadow_color), shadow_thickness, shadow_offset, draw_flags, shape_rounding);
+
+                if (wireframe)
+                    draw_list->AddRect(r1, r2, ImGui::GetColorU32(shape_color), shape_rounding);
+                else
+                    draw_list->AddRectFilled(r1, r2, ImGui::GetColorU32(shape_color), shape_rounding);
+            }
+
+            ImGui::SameLine();
+
+            // Circle
+            {
+                ImVec2 p = ImGui::GetCursorScreenPos();
+                ImGui::Dummy(ImVec2(200.0f, 200.0f));
+
+                // FIXME-SHADOWS: Offset forced to zero when shadow is not filled because it isn't supported
+                float off = 10.0f;
+                ImVec2 r1(p.x + 50.0f + off, p.y + 50.0f + off);
+                ImVec2 r2(p.x + 150.0f - off, p.y + 150.0f - off);
+                ImVec2 center(p.x + 100.0f, p.y + 100.0f);
+                ImDrawFlags draw_flags = shadow_filled ? ImDrawFlags_None : ImDrawFlags_ShadowCutOutShapeBackground;
+                draw_list->AddShadowCircle(center, 50.0f, ImGui::GetColorU32(shadow_color), shadow_thickness, shadow_filled ? shadow_offset : ImVec2(0.0f, 0.0f), draw_flags, 0);
+
+                if (wireframe)
+                    draw_list->AddCircle(center, 50.0f, ImGui::GetColorU32(shape_color), 0);
+                else
+                    draw_list->AddCircleFilled(center, 50.0f, ImGui::GetColorU32(shape_color), 0);
+            }
+
+            ImGui::SameLine();
+
+            // Convex shape
+            {
+                ImVec2 pos = ImGui::GetCursorScreenPos();
+                ImGui::Dummy(ImVec2(200.0f, 200.0f));
+
+                const ImVec2 poly_centre(pos.x + 50.0f, pos.y + 100.0f);
+                ImVec2 poly_points[8];
+                int poly_points_count = 0;
+
+                switch (poly_shape_index)
+                {
+                default:
+                case 0:
+                {
+                    poly_points[0] = ImVec2(poly_centre.x - 32.0f, poly_centre.y);
+                    poly_points[1] = ImVec2(poly_centre.x - 24.0f, poly_centre.y + 24.0f);
+                    poly_points[2] = ImVec2(poly_centre.x, poly_centre.y + 32.0f);
+                    poly_points[3] = ImVec2(poly_centre.x + 24.0f, poly_centre.y + 24.0f);
+                    poly_points[4] = ImVec2(poly_centre.x + 32.0f, poly_centre.y);
+                    poly_points[5] = ImVec2(poly_centre.x + 24.0f, poly_centre.y - 24.0f);
+                    poly_points[6] = ImVec2(poly_centre.x, poly_centre.y - 32.0f);
+                    poly_points[7] = ImVec2(poly_centre.x - 32.0f, poly_centre.y - 32.0f);
+                    poly_points_count = 8;
+                    break;
+                }
+                case 1:
+                {
+                    poly_points[0] = ImVec2(poly_centre.x + 40.0f, poly_centre.y - 20.0f);
+                    poly_points[1] = ImVec2(poly_centre.x, poly_centre.y + 32.0f);
+                    poly_points[2] = ImVec2(poly_centre.x - 24.0f, poly_centre.y - 32.0f);
+                    poly_points_count = 3;
+                    break;
+                }
+                case 2:
+                {
+                    poly_points[0] = ImVec2(poly_centre.x - 32.0f, poly_centre.y);
+                    poly_points[1] = ImVec2(poly_centre.x, poly_centre.y + 32.0f);
+                    poly_points[2] = ImVec2(poly_centre.x + 32.0f, poly_centre.y);
+                    poly_points[3] = ImVec2(poly_centre.x, poly_centre.y - 32.0f);
+                    poly_points_count = 4;
+                    break;
+                }
+                case 3:
+                {
+                    poly_points[0] = ImVec2(poly_centre.x - 4.0f, poly_centre.y - 20.0f);
+                    poly_points[1] = ImVec2(poly_centre.x + 12.0f, poly_centre.y + 2.0f);
+                    poly_points[2] = ImVec2(poly_centre.x + 8.0f, poly_centre.y + 16.0f);
+                    poly_points[3] = ImVec2(poly_centre.x, poly_centre.y + 32.0f);
+                    poly_points[4] = ImVec2(poly_centre.x - 16.0f, poly_centre.y - 32.0f);
+                    poly_points_count = 5;
+                    break;
+                }
+                case 4: // Same as test case 3 but with reversed winding
+                {
+                    poly_points[0] = ImVec2(poly_centre.x - 16.0f, poly_centre.y - 32.0f);
+                    poly_points[1] = ImVec2(poly_centre.x, poly_centre.y + 32.0f);
+                    poly_points[2] = ImVec2(poly_centre.x + 8.0f, poly_centre.y + 16.0f);
+                    poly_points[3] = ImVec2(poly_centre.x + 12.0f, poly_centre.y + 2.0f);
+                    poly_points[4] = ImVec2(poly_centre.x - 4.0f, poly_centre.y - 20.0f);
+                    poly_points_count = 5;
+                    break;
+                }
+                }
+
+                // FIXME-SHADOWS: Offset forced to zero when shadow is not filled because it isn't supported
+                ImDrawFlags draw_flags = shadow_filled ? ImDrawFlags_None : ImDrawFlags_ShadowCutOutShapeBackground;
+                draw_list->AddShadowConvexPoly(poly_points, poly_points_count, ImGui::GetColorU32(shadow_color), shadow_thickness, shadow_filled ? shadow_offset : ImVec2(0.0f, 0.0f), draw_flags);
+
+                if (wireframe)
+                    draw_list->AddPolyline(poly_points, poly_points_count, ImGui::GetColorU32(shape_color), true, 1.0f);
+                else
+                    draw_list->AddConvexPolyFilled(poly_points, poly_points_count, ImGui::GetColorU32(shape_color));
+            }
+
+            draw_list->Flags = old_flags;
+
+            ImGui::EndTabItem();
+        }
+
         if (ImGui::BeginTabItem("BG/FG draw lists"))
         {
             static bool draw_bg = true;

imgui_internal.h

@@ -170,6 +170,7 @@ struct ImGuiOldColumns;             // Storage data for a columns set for legacy
 struct ImGuiPopupData;              // Storage for current popup stack
 struct ImGuiSettingsHandler;        // Storage for one type registered in the .ini file
 struct ImGuiStyleMod;               // Stacked style modifier, backup of modified data so we can restore it
+struct ImGuiStyleShadowTexConfig;   // Shadow Texture baking config
 struct ImGuiStyleVarInfo;           // Style variable information (e.g. to access style variables from an enum)
 struct ImGuiTabBar;                 // Storage for a tab bar
 struct ImGuiTabItem;                // Storage for a tab item (within a tab bar)
@@ -497,6 +498,7 @@ inline ImVec4 ImLerp(const ImVec4& a, const ImVec4& b, float t)         { return
 inline float  ImSaturate(float f)                                       { return (f < 0.0f) ? 0.0f : (f > 1.0f) ? 1.0f : f; }
 inline float  ImLengthSqr(const ImVec2& lhs)                            { return (lhs.x * lhs.x) + (lhs.y * lhs.y); }
 inline float  ImLengthSqr(const ImVec4& lhs)                            { return (lhs.x * lhs.x) + (lhs.y * lhs.y) + (lhs.z * lhs.z) + (lhs.w * lhs.w); }
+inline float  ImLength(const ImVec2& lhs, float fail_value)             { float d = (lhs.x * lhs.x) + (lhs.y * lhs.y); if (d > 0.0f) return ImSqrt(d); return fail_value; }
 inline float  ImInvLength(const ImVec2& lhs, float fail_value)          { float d = (lhs.x * lhs.x) + (lhs.y * lhs.y); if (d > 0.0f) return ImRsqrt(d); return fail_value; }
 inline float  ImTrunc(float f)                                          { return (float)(int)(f); }
 inline ImVec2 ImTrunc(const ImVec2& v)                                  { return ImVec2((float)(int)(v.x), (float)(int)(v.y)); }
@@ -856,6 +858,9 @@ struct IMGUI_API ImDrawListSharedData
     float           ArcFastRadiusCutoff;                        // Cutoff radius after which arc drawing will fallback to slower PathArcTo()
     ImU8            CircleSegmentCounts[64];    // Precomputed segment count for given radius before we calculate it dynamically (to avoid calculation overhead)
 
+    int*            ShadowRectIds;              // IDs of rects for shadow texture (2 entries)
+    const ImVec4*   ShadowRectUvs;              // UV coordinates for shadow texture (10 entries)
+
     ImDrawListSharedData();
     ~ImDrawListSharedData();
     void SetCircleTessellationMaxError(float max_error);

imgui_widgets.cpp

@@ -8929,10 +8929,14 @@ bool ImGui::BeginViewportSideBar(const char* name, ImGuiViewport* viewport_p, Im
     }
 
     window_flags |= ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove;
+
+    // Create window
+    PushStyleColor(ImGuiCol_WindowShadow, ImVec4(0, 0, 0, 0));
     PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
     PushStyleVar(ImGuiStyleVar_WindowMinSize, ImVec2(0, 0)); // Lift normal size constraint
     bool is_open = Begin(name, NULL, window_flags);
     PopStyleVar(2);
+    PopStyleColor();
 
     return is_open;
 }