Revert changing default value of ImTextureID_Invalid to -1. Back to 0. (#9295, #9310, #9293, #8745, #8465, #7090)

Reverts 0db591935f

docs/CHANGELOG.txt

@@ -41,16 +41,6 @@ HOW TO UPDATE?
 
 Breaking Changes:
 
- - Changed default ImTextureID_Invalid value to -1 instead of 0 if not #define-d.
-    (#9293, #8745, #8465, #7090)
-   - It seems like a better default since it will work with backends storing
-     indices or memory offsets inside ImTextureID, where 0 might be a valid value.
-   - If this is causing problem with e.g your custom ImTextureID definition, you can
-     add '#define ImTextureID_Invalid 0' to your imconfig.h + PLEASE report this to GitHub.
-   - If you have hardcoded e.g. 'if (tex_id == 0)' checks they should be updated.
-     e.g. OpenGL2, OpenGL3 and SDLRenderer3 backends incorrectly had 'IM_ASSERT(tex->TexID == 0)'
-     lines which were replaced with 'IM_ASSERT(tex->TexID == ImTextureID_Invalid)'.
-     If you have copied or forked backends consider fixing locally. (#9295)
  - Separator(): fixed a legacy quirk where Separator() was submitting a zero-height
    item for layout purpose, even though it draws a 1-pixel separator.
    The fix could affect code e.g. computing height from multiple widgets in order to

imgui.cpp

@@ -395,10 +395,6 @@ IMPLEMENTING SUPPORT for ImGuiBackendFlags_RendererHasTextures:
  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.
 
- - 2026/03/12 (1.92.7) - Changed default ImTextureID_Invalid to -1 instead of 0 if not #define-d. (#9293, #8745, #8465, #7090)
-                         It seems like a better default since it will work with backends storing indices or memory offsets inside ImTextureID, where 0 might be a valid value.
-                         If this is causing problem with e.g. your custom ImTextureID definition, you can add '#define ImTextureID_Invalid 0' to your imconfig.h + PLEASE report this to GitHub.
-                         If you have hard-coded e.g. 'if (tex_id == 0)' checks they should be updated. e.g. OpenGL2, OpenGL3 and SDLRenderer3 backends incorrectly had 'IM_ASSERT(tex->TexID == 0)' lines which were replaced with 'IM_ASSERT(tex->TexID == ImTextureID_Invalid)'. (#9295)
  - 2026/02/26 (1.92.7) - Separator: fixed a legacy quirk where Separator() was submitting a zero-height item for layout purpose, even though it draws a 1-pixel separator.
                          The fix could affect code e.g. computing height from multiple widgets in order to allocate vertical space for a footer or multi-line status bar. (#2657, #9263)
                          The "Console" example had such a bug:

imgui.h

@@ -341,10 +341,10 @@ typedef ImU64 ImTextureID;      // Default: store up to 64-bits (any pointer or
 #endif
 
 // Define this if you need to change the invalid value for your backend.
-// - in v1.92.7 (2025/03/12): we changed default value from 0 to -1 as it is a better default, which supports storing offsets/indices.
-// - If this is causing problem with your custom ImTextureID definition, you can add '#define ImTextureID_Invalid' to your imconfig + please report this to GitHub.
+// - If your backend is using ImTextureID to store an index/offset and you need 0 to be valid, You can add '#define ImTextureID_Invalid ((ImTextureID)-1)' in your imconfig.h file.
+// - From 2026/03/12 to 2026/03/19 we experimented with changing to default to -1, but I worried it would cause too many issues in third-party code so it was reverted.
 #ifndef ImTextureID_Invalid
-#define ImTextureID_Invalid     ((ImTextureID)-1)
+#define ImTextureID_Invalid     ((ImTextureID)0)
 #endif
 
 // ImTextureRef = higher-level identifier for a texture. Store a ImTextureID _or_ a ImTextureData*.
@@ -3909,8 +3909,8 @@ inline ImTextureID ImTextureRef::GetTexID() const
 // Using an indirection to avoid patching ImDrawCmd after a SetTexID() call (but this could be an alternative solution too)
 inline ImTextureID ImDrawCmd::GetTexID() const
 {
-    // If you are getting this assert with ImTextureID_Invalid == 0 and your ImTextureID is used to store an index:
-    // - You can add '#define ImTextureID_Invalid ((ImTextureID)-1)' in your imconfig file.
+    // If you are getting this assert with ImTextureID_Invalid == 0 and your ImTextureID is used to store an index or an offset:
+    // - You can add '#define ImTextureID_Invalid ((ImTextureID)-1)' in your imconfig.h file.
     // If you are getting this assert with a renderer backend with support for ImGuiBackendFlags_RendererHasTextures (1.92+):
     // - You must correctly iterate and handle ImTextureData requests stored in ImDrawData::Textures[]. See docs/BACKENDS.md.
     ImTextureID tex_id = TexRef._TexData ? TexRef._TexData->TexID : TexRef._TexID; // == TexRef.GetTexID() above.