Backends: GL3: Fix compile for < 3.2 bindings where glDrawElementsBaseVertex is not available. (#2866, #2852)
diff --git a/examples/imgui_impl_opengl3.cpp b/examples/imgui_impl_opengl3.cpp
index 3824647..7f2c588 100644
--- a/examples/imgui_impl_opengl3.cpp
+++ b/examples/imgui_impl_opengl3.cpp
@@ -120,14 +120,15 @@
#endif
// Desktop GL has glDrawElementsBaseVertex() which GL ES and WebGL don't have.
-#if defined(IMGUI_IMPL_OPENGL_ES2) || defined(IMGUI_IMPL_OPENGL_ES3)
-#define IMGUI_IMPL_OPENGL_HAS_DRAW_WITH_BASE_VERTEX 0
+#if defined(IMGUI_IMPL_OPENGL_ES2) || defined(IMGUI_IMPL_OPENGL_ES3) || !defined(GL_VERSION_3_2)
+#define IMGUI_IMPL_OPENGL_MAY_HAVE_DRAW_WITH_BASE_VERTEX 0
#else
-#define IMGUI_IMPL_OPENGL_HAS_DRAW_WITH_BASE_VERTEX 1
+#define IMGUI_IMPL_OPENGL_MAY_HAVE_DRAW_WITH_BASE_VERTEX 1
#endif
// OpenGL Data
static char g_GlslVersionString[32] = "";
+static GLuint g_GlVersion = 0;
static GLuint g_FontTexture = 0;
static GLuint g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
static int g_AttribLocationTex = 0, g_AttribLocationProjMtx = 0; // Uniforms location
@@ -137,11 +138,22 @@
// Functions
bool ImGui_ImplOpenGL3_Init(const char* glsl_version)
{
+ // query for GL version
+#if !defined(IMGUI_IMPL_OPENGL_ES2)
+ GLint major, minor;
+ glGetIntegerv (GL_MAJOR_VERSION, &major);
+ glGetIntegerv (GL_MINOR_VERSION, &minor);
+ g_GlVersion = major * 1000 + minor;
+#else
+ g_GlVersion = 2000; // GLES 2
+#endif
+
// Setup back-end capabilities flags
ImGuiIO& io = ImGui::GetIO();
io.BackendRendererName = "imgui_impl_opengl3";
-#if IMGUI_IMPL_OPENGL_HAS_DRAW_WITH_BASE_VERTEX
- io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset; // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
+#if IMGUI_IMPL_OPENGL_MAY_HAVE_DRAW_WITH_BASE_VERTEX
+ if (g_GlVersion >= 3200)
+ io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset; // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
#endif
// Store GLSL version string so we can refer to it later in case we recreate shaders. Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
@@ -344,8 +356,11 @@
// Bind texture, Draw
glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
-#if IMGUI_IMPL_OPENGL_HAS_DRAW_WITH_BASE_VERTEX
- glDrawElementsBaseVertex(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, (void*)(intptr_t)(pcmd->IdxOffset * sizeof(ImDrawIdx)), (GLint)pcmd->VtxOffset);
+#if IMGUI_IMPL_OPENGL_MAY_HAVE_DRAW_WITH_BASE_VERTEX
+ if (g_GlVersion >= 3200)
+ glDrawElementsBaseVertex(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, (void*)(intptr_t)(pcmd->IdxOffset * sizeof(ImDrawIdx)), (GLint)pcmd->VtxOffset);
+ else
+ glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, (void*)(intptr_t)(pcmd->IdxOffset * sizeof(ImDrawIdx)));
#else
glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, (void*)(intptr_t)(pcmd->IdxOffset * sizeof(ImDrawIdx)));
#endif