Backends: OpenGL3: Using buffer orphaning + glBufferSubData(), seems to fix leaks with multi-viewports with some Intel HD drivers.. (#4468, #4504, #2981, #3381)

backends/imgui_impl_opengl3.cpp

@@ -14,6 +14,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-12-15: OpenGL: Using buffer orphaning + glBufferSubData(), seems to fix leaks with multi-viewports with some Intel HD drivers.
 //  2021-08-23: OpenGL: Fixed ES 3.0 shader ("#version 300 es") use normal precision floats to avoid wobbly rendering at HD resolutions.
 //  2021-08-19: OpenGL: Embed and use our own minimal GL loader (imgui_impl_opengl3_loader.h), removing requirement and support for third-party loader.
 //  2021-06-29: Reorganized backend to pull data from a single structure to facilitate usage with multiple-contexts (all g_XXXX access changed to bd->XXXX).
@@ -174,6 +175,8 @@ struct ImGui_ImplOpenGL3_Data
     GLuint          AttribLocationVtxUV;
     GLuint          AttribLocationVtxColor;
     unsigned int    VboHandle, ElementsHandle;
+    GLsizeiptr      VertexBufferSize;
+    GLsizeiptr      IndexBufferSize;
     bool            HasClipOrigin;
 
     ImGui_ImplOpenGL3_Data() { memset(this, 0, sizeof(*this)); }
@@ -425,8 +428,20 @@ void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
 
         // Upload vertex/index buffers
-        glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)cmd_list->VtxBuffer.Size * (int)sizeof(ImDrawVert), (const GLvoid*)cmd_list->VtxBuffer.Data, GL_STREAM_DRAW);
-        glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)cmd_list->IdxBuffer.Size * (int)sizeof(ImDrawIdx), (const GLvoid*)cmd_list->IdxBuffer.Data, GL_STREAM_DRAW);
+        GLsizeiptr vtx_buffer_size = (GLsizeiptr)cmd_list->VtxBuffer.Size * (int)sizeof(ImDrawVert);
+        GLsizeiptr idx_buffer_size = (GLsizeiptr)cmd_list->IdxBuffer.Size * (int)sizeof(ImDrawIdx);
+        if (bd->VertexBufferSize < vtx_buffer_size)
+        {
+            bd->VertexBufferSize = vtx_buffer_size;
+            glBufferData(GL_ARRAY_BUFFER, bd->VertexBufferSize, NULL, GL_STREAM_DRAW);
+        }
+        if (bd->IndexBufferSize < idx_buffer_size)
+        {
+            bd->IndexBufferSize = idx_buffer_size;
+            glBufferData(GL_ELEMENT_ARRAY_BUFFER, bd->IndexBufferSize, NULL, GL_STREAM_DRAW);
+        }
+        glBufferSubData(GL_ARRAY_BUFFER, 0, vtx_buffer_size, (const GLvoid*)cmd_list->VtxBuffer.Data);
+        glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, idx_buffer_size, (const GLvoid*)cmd_list->IdxBuffer.Data);
 
         for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
         {

backends/imgui_impl_opengl3_loader.h

@@ -249,11 +249,13 @@ typedef void (APIENTRYP PFNGLBINDBUFFERPROC) (GLenum target, GLuint buffer);
 typedef void (APIENTRYP PFNGLDELETEBUFFERSPROC) (GLsizei n, const GLuint *buffers);
 typedef void (APIENTRYP PFNGLGENBUFFERSPROC) (GLsizei n, GLuint *buffers);
 typedef void (APIENTRYP PFNGLBUFFERDATAPROC) (GLenum target, GLsizeiptr size, const void *data, GLenum usage);
+typedef void (APIENTRYP PFNGLBUFFERSUBDATAPROC) (GLenum target, GLintptr offset, GLsizeiptr size, const void *data);
 #ifdef GL_GLEXT_PROTOTYPES
 GLAPI void APIENTRY glBindBuffer (GLenum target, GLuint buffer);
 GLAPI void APIENTRY glDeleteBuffers (GLsizei n, const GLuint *buffers);
 GLAPI void APIENTRY glGenBuffers (GLsizei n, GLuint *buffers);
 GLAPI void APIENTRY glBufferData (GLenum target, GLsizeiptr size, const void *data, GLenum usage);
+GLAPI void APIENTRY glBufferSubData (GLenum target, GLintptr offset, GLsizeiptr size, const void *data);
 #endif
 #endif /* GL_VERSION_1_5 */
 #ifndef GL_VERSION_2_0
@@ -447,6 +449,7 @@ union GL3WProcs {
         PFNGLBLENDEQUATIONSEPARATEPROC   BlendEquationSeparate;
         PFNGLBLENDFUNCSEPARATEPROC       BlendFuncSeparate;
         PFNGLBUFFERDATAPROC              BufferData;
+        PFNGLBUFFERSUBDATAPROC           BufferSubData;
         PFNGLCLEARPROC                   Clear;
         PFNGLCLEARCOLORPROC              ClearColor;
         PFNGLCOMPILESHADERPROC           CompileShader;
@@ -506,6 +509,7 @@ GL3W_API extern union GL3WProcs imgl3wProcs;
 #define glBlendEquationSeparate          imgl3wProcs.gl.BlendEquationSeparate
 #define glBlendFuncSeparate              imgl3wProcs.gl.BlendFuncSeparate
 #define glBufferData                     imgl3wProcs.gl.BufferData
+#define glBufferSubData                  imgl3wProcs.gl.BufferSubData
 #define glClear                          imgl3wProcs.gl.Clear
 #define glClearColor                     imgl3wProcs.gl.ClearColor
 #define glCompileShader                  imgl3wProcs.gl.CompileShader
@@ -692,6 +696,7 @@ static const char *proc_names[] = {
     "glBlendEquationSeparate",
     "glBlendFuncSeparate",
     "glBufferData",
+    "glBufferSubData",
     "glClear",
     "glClearColor",
     "glCompileShader",

docs/CHANGELOG.txt

@@ -105,6 +105,8 @@ Other Changes:
 - Backends: Vulkan: Call vkCmdSetScissor() at the end of render with a full-viewport to reduce
   likehood of issues with people using VK_DYNAMIC_STATE_SCISSOR in their app without calling
   vkCmdSetScissor() explicitly every frame. (#4644)
+- Backends: OpenGL3: Using buffer orphaning + glBufferSubData(), seems to fix leaks with multi-viewports
+  with some Intel HD drivers, and perhaps improve performances. (#4468, #4504, #2981, #3381) [@parbo]
 - Backends: OpenGL2, Allegro5, Marmalade: Fixed mishandling of the ImDrawCmd::IdxOffset field.
   This is an old bug, but due to the way we created drawlists, it never had any visible side-effect before.
   The new code for handling Modal and CTRL+Tab dimming/whitening recently made the bug surface. (#4790)

imgui_widgets.cpp

@@ -6882,7 +6882,7 @@ static bool IsRootOfOpenMenuSet()
     // Instead we don't treat Popup specifically (in order to consistently support menu features in them), maybe the first child menu of a Popup
     // doesn't have the _ChildWindow flag, and we rely on this IsRootOfOpenMenuSet() check to allow hovering between root window/popup and first chilld menu.
     const ImGuiPopupData* upper_popup = &g.OpenPopupStack[g.BeginPopupStack.Size];
-    return (upper_popup && /*upper_popup->OpenParentId == window->IDStack.back() &&*/ upper_popup->Window && (upper_popup->Window->Flags & ImGuiWindowFlags_ChildMenu));
+    return (/*upper_popup->OpenParentId == window->IDStack.back() &&*/ upper_popup->Window && (upper_popup->Window->Flags & ImGuiWindowFlags_ChildMenu));
 }
 
 bool ImGui::BeginMenuEx(const char* label, const char* icon, bool enabled)