Examples: OpenGL3: simplified code. Upload each vertex array separately. (cf #264)

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -56,38 +56,29 @@ static void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
     glUseProgram(g_ShaderHandle);
     glUniform1i(g_AttribLocationTex, 0);
     glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);
-
-    // Grow our buffer according to what we need
-    glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
-    int needed_vtx_size = draw_data->TotalVtxCount * sizeof(ImDrawVert);
-    if (g_VboSize < needed_vtx_size)
-    {
-        g_VboSize = needed_vtx_size + 5000 * sizeof(ImDrawVert);  // Grow buffer
-        glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)g_VboSize, NULL, GL_STREAM_DRAW);
-    }
-
-    // Copy and convert all vertices into a single contiguous buffer
-    unsigned char* vtx_data = (unsigned char*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
-    if (!vtx_data)
-        return;
-    for (int n = 0; n < draw_data->CmdListsCount; n++)
-    {
-        const ImDrawList* cmd_list = draw_data->CmdLists[n];
-        memcpy(vtx_data, &cmd_list->VtxBuffer[0], cmd_list->VtxBuffer.size() * sizeof(ImDrawVert));
-        vtx_data += cmd_list->VtxBuffer.size() * sizeof(ImDrawVert);
-    }
-    glUnmapBuffer(GL_ARRAY_BUFFER);
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
     glBindVertexArray(g_VaoHandle);
 
-    int vtx_offset = 0;
     for (int n = 0; n < draw_data->CmdListsCount; n++)
     {
         const ImDrawList* cmd_list = draw_data->CmdLists[n];
         const ImDrawIdx* idx_buffer = &cmd_list->IdxBuffer.front();
 
-        const ImDrawCmd* pcmd_end = cmd_list->CmdBuffer.end();
-        for (const ImDrawCmd* pcmd = cmd_list->CmdBuffer.begin(); pcmd != pcmd_end; pcmd++)
+        glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
+        int needed_vtx_size = cmd_list->VtxBuffer.size() * sizeof(ImDrawVert);
+        if (g_VboSize < needed_vtx_size)
+        {
+            // Grow our buffer if needed
+            g_VboSize = needed_vtx_size + 2000 * sizeof(ImDrawVert);
+            glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)g_VboSize, NULL, GL_STREAM_DRAW);
+        }
+
+        unsigned char* vtx_data = (unsigned char*)glMapBufferRange(GL_ARRAY_BUFFER, 0, needed_vtx_size, GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT);
+        if (!vtx_data)
+            continue;
+        memcpy(vtx_data, &cmd_list->VtxBuffer[0], cmd_list->VtxBuffer.size() * sizeof(ImDrawVert));
+        glUnmapBuffer(GL_ARRAY_BUFFER);
+
+        for (const ImDrawCmd* pcmd = cmd_list->CmdBuffer.begin(); pcmd != cmd_list->CmdBuffer.end(); pcmd++)
         {
             if (pcmd->UserCallback)
             {
@@ -97,15 +88,15 @@ static void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
             {
                 glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
                 glScissor((int)pcmd->ClipRect.x, (int)(height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
-                glDrawElementsBaseVertex(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer, vtx_offset);
+                glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer);
             }
             idx_buffer += pcmd->ElemCount;
         }
-        vtx_offset += cmd_list->VtxBuffer.size();
     }
 
     // Restore modified state
     glBindVertexArray(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
     glUseProgram(last_program);
     glDisable(GL_SCISSOR_TEST);
     glBindTexture(GL_TEXTURE_2D, last_texture);