Docs: retroactively amend 1.92.8 changelog about ImDrawFlags_Closed value.

Amend 6df50a0

docs/CHANGELOG.txt

@@ -98,6 +98,9 @@ Breaking Changes:
 - DrawList: obsoleted `ImDrawCallback_ResetRenderState` in favor of using `ImGui::GetPlatformIO().DrawCallback_ResetRenderState`,
     which is part of our new standard draw callbacks. (#9378)
     Redirecting the earlier value into the later one when set, so both old and new code should work.
+- DrawList: changed value of `ImDrawFlags_Closed`. It was previously advertised as "always == 1" when introduced
+  in 1.82 (2021/02), in order to facilitate backward compatibility with the legacy `bool closed` flag. This
+  guarantee has been removed. The bit is reserved, and `AddPolyline()`, `PathStroke()` will assert when it is used.
 - Backends:
   - Vulkan: redesigned to use separate ImageView + Sampler instead of Combined Image Sampler. (#914)
     This change allows us to facilitate changing samplers, in line with other backends. [@yaz0r, @ocornut]

imgui.cpp

@@ -416,6 +416,8 @@ IMPLEMENTING SUPPORT for ImGuiBackendFlags_RendererHasTextures:
                            The new order is also more convenient as `flags` are less frequently used than `thickness` in real code.
                          - As a general policy in Dear ImGui, all our flags default to 0 so ImDrawFlags_None was likely written 0 in some call sites.
                          - Consider adding `#define IMGUI_DISABLE_OBSOLETE_FUNCTIONS` in your imconfig.h, even temporarily, to clean up legacy code.
+ - 2026/05/07 (1.92.8) - DrawList: changed value of `ImDrawFlags_Closed`. It was previously advertised as "always == 1" when introduced in 1.82 (2021/02), in order to facilitate backward compatibility with the legacy `bool closed` flag.
+                         This guarantee has been removed. The bit is reserved and `AddPolyline()`, `PathStroke()` will assert when it is used.
  - 2026/04/23 (1.92.8) - DrawList: obsoleted `ImDrawCallback_ResetRenderState` in favor of using `ImGui::GetPlatformIO().DrawCallback_ResetRenderState`, which is part of our new standard draw callbacks. (#9378)
  - 2026/04/22 (1.92.8) - Backends: Vulkan: redesigned to use separate ImageView + Sampler instead of Combined Image Sampler.
                          - When registering custom textures: changed ImGui_ImplVulkan_AddTexture() signature to remove Sampler.

imgui.h

@@ -3263,7 +3263,10 @@ enum ImDrawFlags_
     ImDrawFlags_RoundCornersRight           = ImDrawFlags_RoundCornersBottomRight | ImDrawFlags_RoundCornersTopRight,
     ImDrawFlags_RoundCornersMask_           = ImDrawFlags_RoundCornersAll | ImDrawFlags_RoundCornersNone,
 
+    // Stroke options
     ImDrawFlags_Closed                      = 1 << 9, // PathStroke(), AddPolyline(): specify that shape should be closed.
+    //ImDrawFlags_Closed                    = 1 << 0, // Prior to 1.92.8 (May 2026), ImDrawFlags_Closed was guaranteed to be == 1<<0 == 1 for legacy compatibility reason. Hardcoded use of 1 or true should be replaced.
+
     ImDrawFlags_InvalidMask_                = ~0x7FFFFFF0, // == 0x8000000F,
 };
 

imgui_draw.cpp

@@ -823,6 +823,11 @@ void ImDrawList::AddPolyline(const ImVec2* points, const int points_count, ImU32
     const ImVec2 opaque_uv = _Data->TexUvWhitePixel;
     const int count = closed ? points_count : points_count - 1; // The number of line segments we need to draw
     const bool thick_line = (thickness > _FringeScale);
+
+    // If this assert triggers on legacy code:
+    // - 1.92.8 (2025/05): swapped two last parameters order: flags, thickness --> thickness, flags. This should normally be caught by compile-time type-checking.
+    // - 1.92.8 (2025/05): changed value of ImDrawList_Closed which was previously guaranteed to be == 1. Hardcoded use of 1 or true should be replaced.
+    // Read more details near AddRect() + see "API BREAKING CHANGES" section for 1.82, 1.90 and 1.92.8.
     IM_ASSERT_USER_ERROR_RET((flags & ImDrawFlags_InvalidMask_) == 0, "Incorrect parameter. Did you swap 'thickness' and 'flags'?");
 
     if (Flags & ImDrawListFlags_AntiAliasedLines)
@@ -1503,13 +1508,14 @@ void ImDrawList::AddLineV(float x, float min_y, float max_y, ImU32 col, float th
 void ImDrawList::AddRect(const ImVec2& p_min, const ImVec2& p_max, ImU32 col, float rounding, float thickness, ImDrawFlags flags)
 {
     // If this assert triggers on legacy code:
-    // - 1.92.8 (2025/04): swapped two last parameters order: flags, thickness --> thickness, flags. This should normally be caught by compile-time type-checking. 
+    // - 1.92.8 (2025/05): swapped two last parameters order: flags, thickness --> thickness, flags. This should normally be caught by compile-time type-checking.
+    // - 1.92.8 (2025/05): changed value of ImDrawList_Closed which was previously guaranteed to be == 1. Hardcoded use of 1 or true should be replaced.
     // - 1.82.0 (2021/03): changed ImDrawCornerFlags to ImDrawFlags_RoundCornersXXX values.
     //   If you used hard-coded 1 to 15 or ~0 in flags to configure corner rounding use the new flags!
     //   - Hard coded support for ~0 == ImDrawFlags_RoundCornersAll.
     //   - Hard coded support for values 0x01 to 0x0F (matching 15 out of 16 old flags combinations) --> see FixRectCornerFlags() in <1.90 code.
     //   - Hard coded 0x00 with 'float rounding > 0.0f' --> replace with ImDrawFlags_RoundCornersNone or use 'float rounding = 0.0f'.
-    //   See "API BREAKING CHANGES" section for 1.82 and 1.90.
+    //   See "API BREAKING CHANGES" section for 1.82, 1.90 and 1.92.8.
     IM_ASSERT_USER_ERROR_RET((flags & ImDrawFlags_InvalidMask_) == 0, "Incorrect parameter. Did you swap 'thickness' and 'flags'?"); // Or misuse of legacy hard-coded ImDrawCornerFlags values
 
     if ((col & IM_COL32_A_MASK) == 0)