add openGL3 impl (still failing)

1 files changed, 443 insertions, 0 deletions

diff --git a/src/gl3_impl.zig b/src/gl3_impl.zig
new file mode 100644
index 0000000..0d88621
--- /dev/null
+++ b/src/gl3_impl.zig
@@ -0,0 +1,443 @@
+const c = @import("c.zig");
+const mem = @import("std").mem;
+const math = @import("std").math;
+const debug = @import("std").debug;
+const builtin = @import("builtin");
+
+const OpenGLHasDrawWithBaseVertex = @hasField(c, "IMGUI_IMPL_OPENGL_ES2") or
+                                    @hasField(c, "IMGUI_IMPL_OPENGL_ES3");
+
+// OpenGL Data
+var g_GlslVersionString_buf : [32]u8 = undefined;
+var g_GlslVersionString : []u8 = g_GlslVersionString_buf[0..0];
+
+var g_FontTexture : c.GLuint = 0;
+var g_ShaderHandle : c.GLuint = 0;
+var g_VertHandle : c.GLuint = 0;
+var g_FragHandle: c.GLuint = 0;
+var g_AttribLocationTex : c.GLint = 0;
+var g_AttribLocationProjMtx : c.GLint = 0;
+var g_AttribLocationVtxPos : c.GLint = 0;
+var g_AttribLocationVtxUV : c.GLint = 0;
+var g_AttribLocationVtxColor : c.GLint = 0;
+var g_VboHandle : c.GLuint = 0;
+var g_ElementsHandle : c.GLuint = 0;
+
+pub fn Init() void {
+  const io = c.igGetIO();
+  io.*.BackendRendererName = c"imgui_impl_gl3.zig";
+  if (OpenGLHasDrawWithBaseVertex)
+    io.*.BackendFlags |= @enumToInt(c.ImGuiBackendFlags_RendererHasVtxOffset);
+  // @TODO: Viewports
+  // io.*.BackendFlags |= @enumToInt(c.ImGuiBackendFlags_RendererHasViewports);
+
+  // @TODO: GLSL versions?
+  // g_GlslVersionString = g_GlslVersionString_buf[0..glsl_version.len];
+  // mem.copy(u8, g_GlslVersionString, glsl_version);
+
+  // @FIXME: just for testing:
+  var tex : c.GLint = undefined;
+  c.glGetIntegerv(c.GL_TEXTURE_BINDING_2D, &tex);
+
+  // @TODO: Viewports
+  // if (io.*.ConfigFlags & @enumToInt(c.ImGuiConfigFlags_ViewportsEnable) != 0)
+  //   InitPlatformInterface();
+}
+
+pub fn Shutdown() void {
+  // ImGui_ImplOpenGL3_ShutdownPlatformInterface();
+  DestroyDeviceObjects();
+}
+
+pub fn NewFrame() !void {
+  if (g_ShaderHandle == 0)
+    try CreateDeviceObjects();
+}
+
+fn CreateDeviceObjects() !void {
+  // back up GL state
+  var last_texture : c.GLint = undefined;
+  var last_array_buffer : c.GLint = undefined;
+  var last_vertex_array : c.GLint = undefined;
+
+  c.glGetIntegerv(c.GL_TEXTURE_BINDING_2D, &last_texture);
+  defer c.glBindTexture(c.GL_TEXTURE_2D, @intCast(c.GLuint, last_texture));
+
+  c.glGetIntegerv(c.GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
+  c.glBindBuffer(c.GL_ARRAY_BUFFER, @intCast(c.GLuint, last_array_buffer));
+
+  if (!@hasField(c, "IMGUI_IMPL_OPENGL_ES2"))
+    c.glGetIntegerv(c.GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
+  defer if (!@hasField(c, "IMGUI_IMPL_OPENGL_ES2"))
+    c.glBindVertexArray(@intCast(c.GLuint, last_vertex_array));
+
+  // @TODO: GLSL versions?
+  const vertex_shader_glsl : [*]const c.GLchar =
+    c\\#version 150
+    c\\uniform mat4 ProjMtx;
+    c\\in vec2 Position;
+    c\\in vec2 UV;
+    c\\in vec4 Color;
+    c\\out vec2 Frag_UV;
+    c\\out vec4 Frag_Color;
+    c\\void main()
+    c\\{
+    c\\    Frag_UV = UV;
+    c\\    Frag_Color = Color;
+    c\\    gl_Position = ProjMtx * vec4(Position.xy, 0, 1);
+    c\\}
+  ;
+
+  const fragment_shader_glsl : [*]const c.GLchar =
+    c\\#version 150
+    c\\uniform sampler2D Texture;
+    c\\in vec2 Frag_UV;
+    c\\in vec4 Frag_Color;
+    c\\out vec4 Out_Color;
+    c\\void main()
+    c\\{
+    c\\    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);
+    c\\}
+  ;
+
+  // Create shaders / programs
+  g_VertHandle = c.glCreateShader(c.GL_VERTEX_SHADER);
+  c.glShaderSource(g_VertHandle, 1, &vertex_shader_glsl, null);
+  c.glCompileShader(g_VertHandle);
+  try CheckThing(.Shader, g_VertHandle, "vertex shader");
+
+  g_FragHandle = c.glCreateShader(c.GL_FRAGMENT_SHADER);
+  c.glShaderSource(g_FragHandle, 1, &fragment_shader_glsl, null);
+  c.glCompileShader(g_FragHandle);
+  try CheckThing(.Shader, g_FragHandle, "fragment shader");
+
+  g_ShaderHandle = c.glCreateProgram();
+  c.glAttachShader(g_ShaderHandle, g_VertHandle);
+  c.glAttachShader(g_ShaderHandle, g_FragHandle);
+  c.glLinkProgram(g_ShaderHandle);
+  try CheckThing(.Program, g_ShaderHandle, "shader program");
+
+  g_AttribLocationTex = c.glGetUniformLocation(g_ShaderHandle, c"Texture");
+  g_AttribLocationProjMtx = c.glGetUniformLocation(g_ShaderHandle, c"ProjMtx");
+  g_AttribLocationVtxPos = c.glGetAttribLocation(g_ShaderHandle, c"Position");
+  g_AttribLocationVtxUV = c.glGetAttribLocation(g_ShaderHandle, c"UV");
+  g_AttribLocationVtxColor = c.glGetAttribLocation(g_ShaderHandle, c"Color");
+
+  // Create buffers
+  c.glGenBuffers(1, &g_VboHandle);
+  c.glGenBuffers(1, &g_ElementsHandle);
+
+  CreateFontsTexture();
+}
+
+
+const CheckableThing = enum {
+  Shader,
+  Program,
+};
+fn CheckThing(comptime thingType: CheckableThing, handle: c.GLuint, desc: []const u8) !void {
+  var status : c.GLint = undefined;
+  var log_length : c.GLint = undefined;
+  const getInfoLogFunc = switch (thingType) {
+    .Shader => blk: {
+      c.glGetShaderiv(handle, c.GL_COMPILE_STATUS, &status);
+      c.glGetShaderiv(handle, c.GL_INFO_LOG_LENGTH, &log_length);
+      break :blk c.glGetShaderInfoLog;
+    },
+    .Program => blk: {
+      c.glGetProgramiv(handle, c.GL_LINK_STATUS, &status);
+      c.glGetProgramiv(handle, c.GL_INFO_LOG_LENGTH, &log_length);
+      break :blk c.glGetProgramInfoLog;
+    },
+  };
+
+  if (log_length > 1)
+  {
+    var buf : [1024]u8 = undefined;
+    var length : c.GLsizei = undefined;
+    getInfoLogFunc(handle, buf.len, &length, &buf[0]);
+    debug.warn("{}\n", buf[0..@intCast(usize, length)]);
+  }
+
+  if (@intCast(c.GLboolean, status) == c.GL_FALSE) {
+    debug.warn("ERROR: CreateDeviceObjects: failed to compile/link {}! (with GLSL '{}')\n", desc, g_GlslVersionString);
+    return error.ShaderLinkError;
+  }
+}
+
+fn DestroyDeviceObjects() void {
+  if (g_VboHandle != 0) {
+    c.glDeleteBuffers(1, &g_VboHandle);
+    g_VboHandle = 0;
+  }
+
+  if (g_ElementsHandle != 0) {
+    c.glDeleteBuffers(1, &g_ElementsHandle);
+    g_ElementsHandle = 0;
+  }
+
+  if (g_ShaderHandle != 0 and g_VertHandle != 0)
+    c.glDetachShader(g_ShaderHandle, g_VertHandle);
+
+  if (g_ShaderHandle != 0 and g_FragHandle != 0)
+    c.glDetachShader(g_ShaderHandle, g_FragHandle);
+
+  if (g_VertHandle != 0) {
+    c.glDeleteShader(g_VertHandle);
+    g_VertHandle = 0;
+  }
+
+  if (g_FragHandle != 0) {
+    c.glDeleteShader(g_FragHandle);
+    g_FragHandle = 0;
+  }
+
+  if (g_ShaderHandle != 0) {
+    c.glDeleteProgram(g_ShaderHandle);
+    g_ShaderHandle = 0;
+  }
+
+  DestroyFontsTexture();
+}
+
+fn CreateFontsTexture() void {
+  const io = c.igGetIO();
+
+  // Get current font image data
+  var width : c_int = undefined;
+  var height : c_int = undefined;
+  var pixels : [*c]u8 = undefined;
+  c.ImFontAtlas_GetTexDataAsRGBA32(io.*.Fonts, &pixels, &width, &height, null);
+
+  // backup & restore state
+  var last_texture : c.GLint = undefined;
+  c.glGetIntegerv(c.GL_TEXTURE_BINDING_2D, &last_texture);
+  defer c.glBindTexture(c.GL_TEXTURE_2D, @intCast(c.GLuint, last_texture));
+
+  // Upload texture to graphics system
+  c.glGenTextures(1, &g_FontTexture);
+  c.glBindTexture(c.GL_TEXTURE_2D, g_FontTexture);
+  c.glTexParameteri(c.GL_TEXTURE_2D, c.GL_TEXTURE_MIN_FILTER, c.GL_LINEAR);
+  c.glTexParameteri(c.GL_TEXTURE_2D, c.GL_TEXTURE_MAG_FILTER, c.GL_LINEAR);
+  if (@hasField(c, "GL_UNPACK_ROW_LENGTH"))
+    c.glPixelStorei(c.GL_UNPACK_ROW_LENGTH, 0);
+  c.glTexImage2D(c.GL_TEXTURE_2D, 0, c.GL_RGBA, width, height, 0, c.GL_RGBA, c.GL_UNSIGNED_BYTE, pixels);
+
+  // Store texture ID
+  io.*.Fonts.*.TexID = @intToPtr(c.ImTextureID, g_FontTexture);
+}
+
+fn DestroyFontsTexture() void {
+  if (g_FontTexture == 0)
+    return;
+
+  const io = c.igGetIO();
+  c.glDeleteTextures(1, &g_FontTexture);
+  io.*.Fonts.*.TexID = @intToPtr(c.ImTextureID, 0);
+  g_FontTexture = 0;
+}
+
+pub fn RenderDrawData(draw_data : *c.ImDrawData) void {
+  // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
+  const fb_width = @floatToInt(i32, draw_data.*.DisplaySize.x * draw_data.*.FramebufferScale.x);
+  const fb_height = @floatToInt(i32, draw_data.*.DisplaySize.y * draw_data.*.FramebufferScale.y);
+  if (fb_width <= 0 or fb_height <= 0)
+      return;
+
+  // Backup GL state
+  var last_program : c.GLint = undefined;
+  var last_texture : c.GLint = undefined;
+  var last_sampler : c.GLint = undefined;
+  var last_array_buffer : c.GLint = undefined;
+  var last_vertex_array_object : c.GLint = undefined;
+  var last_polygon_mode : [2]c.GLint = undefined;
+  var last_viewport : [4]c.GLint = undefined;
+  var last_scissor_box : [4]c.GLint = undefined;
+  var last_blend_src_rgb : c.GLint = undefined;
+  var last_blend_dst_rgb : c.GLint = undefined;
+  var last_blend_src_alpha : c.GLint = undefined;
+  var last_blend_dst_alpha : c.GLint = undefined;
+  var last_blend_equation_rgb : c.GLint = undefined;
+  var last_blend_equation_alpha : c.GLint = undefined;
+  var clip_origin_lower_left : bool = true;
+  var last_clip_origin : c.GLint = 0;
+  var last_active_texture : c.GLint = undefined;
+
+  c.glGetIntegerv(c.GL_ACTIVE_TEXTURE, &last_active_texture);
+  c.glActiveTexture(c.GL_TEXTURE0);
+  c.glGetIntegerv(c.GL_CURRENT_PROGRAM, &last_program);
+  c.glGetIntegerv(c.GL_TEXTURE_BINDING_2D, &last_texture);
+  if (@hasField(c, "GL_SAMPLER_BINDING"))
+    c.glGetIntegerv(c.GL_SAMPLER_BINDING, &last_sampler);
+  c.glGetIntegerv(c.GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
+  if (!@hasField(c, "IMGUI_IMPL_OPENc.GL_ES2"))
+    c.glGetIntegerv(c.GL_VERTEX_ARRAY_BINDING, &last_vertex_array_object);
+  if (@hasField(c, "GL_POLYGON_MODE"))
+    c.glGetIntegerv(c.GL_POLYGON_MODE, last_polygon_mode);
+  c.glGetIntegerv(c.GL_VIEWPORT, &last_viewport[0]);
+  c.glGetIntegerv(c.GL_SCISSOR_BOX, &last_scissor_box[0]);
+  c.glGetIntegerv(c.GL_BLEND_SRC_RGB, &last_blend_src_rgb);
+  c.glGetIntegerv(c.GL_BLEND_DST_RGB, &last_blend_dst_rgb);
+  c.glGetIntegerv(c.GL_BLEND_SRC_ALPHA, &last_blend_src_alpha);
+  c.glGetIntegerv(c.GL_BLEND_DST_ALPHA, &last_blend_dst_alpha);
+  c.glGetIntegerv(c.GL_BLEND_EQUATION_RGB, &last_blend_equation_rgb);
+  c.glGetIntegerv(c.GL_BLEND_EQUATION_ALPHA, &last_blend_equation_alpha);
+  var last_enable_blend : c.GLboolean = c.glIsEnabled(c.GL_BLEND);
+  var last_enable_cull_face : c.GLboolean = c.glIsEnabled(c.GL_CULL_FACE);
+  var last_enable_depth_test : c.GLboolean = c.glIsEnabled(c.GL_DEPTH_TEST);
+  var last_enable_scissor_test : c.GLboolean = c.glIsEnabled(c.GL_SCISSOR_TEST);
+  if (@hasField(c, "GL_CLIP_ORIGIN") and builtin.os != builtin.Os.osx) {
+    // Support for GL 4.5's glClipControl(GL_UPPER_LEFT)
+    c.glGetIntegerv(c.GL_CLIP_ORIGIN, &last_clip_origin);
+    if (last_clip_origin == c.GL_UPPER_LEFT)
+        clip_origin_lower_left = false;
+  }
+
+  defer {
+    // Restore modified GL state
+    c.glUseProgram(@intCast(c.GLuint, last_program));
+    c.glBindTexture(c.GL_TEXTURE_2D, @intCast(c.GLuint, last_texture));
+    if (@hasField(c, "GL_SAMPLER_BINDING"))
+      c.glBindSampler(0, @intCast(c.GLuint, last_sampler));
+    c.glActiveTexture(@intCast(c.GLuint, last_active_texture));
+    if (!@hasField(c, "IMGUI_IMPL_OPENGL_ES2"))
+      c.glBindVertexArray(@intCast(c.GLuint, last_vertex_array_object));
+    c.glBindBuffer(c.GL_ARRAY_BUFFER, @intCast(c.GLuint, last_array_buffer));
+    c.glBlendEquationSeparate(@intCast(c.GLuint, last_blend_equation_rgb), @intCast(c.GLuint, last_blend_equation_alpha));
+    c.glBlendFuncSeparate(@intCast(c.GLuint, last_blend_src_rgb),
+                          @intCast(c.GLuint, last_blend_dst_rgb),
+                          @intCast(c.GLuint, last_blend_src_alpha),
+                          @intCast(c.GLuint, last_blend_dst_alpha));
+    if (last_enable_blend == c.GL_TRUE) { c.glEnable(c.GL_BLEND); }
+    else { c.glDisable(c.GL_BLEND); }
+    if (last_enable_cull_face == c.GL_TRUE) { c.glEnable(c.GL_CULL_FACE); }
+    else { c.glDisable(c.GL_CULL_FACE); }
+    if (last_enable_depth_test == c.GL_TRUE) { c.glEnable(c.GL_DEPTH_TEST); }
+    else { c.glDisable(c.GL_DEPTH_TEST); }
+    if (last_enable_scissor_test == c.GL_TRUE) { c.glEnable(c.GL_SCISSOR_TEST); }
+    else { c.glDisable(c.GL_SCISSOR_TEST); }
+    if (@hasField(c, "GL_POLYGON_MODE"))
+      c.glPolygonMode(c.GL_FRONT_AND_BACK, @intCast(c.GLenum, last_polygon_mode[0]));
+    c.glViewport(last_viewport[0], last_viewport[1], @intCast(c.GLsizei, last_viewport[2]), @intCast(c.GLsizei, last_viewport[3]));
+    c.glScissor(last_scissor_box[0], last_scissor_box[1], @intCast(c.GLsizei, last_scissor_box[2]), @intCast(c.GLsizei, last_scissor_box[3]));
+  }
+
+  // Setup desired GL state
+  // Recreate the VAO every time (this is to easily allow multiple GL contexts to be rendered to. VAO are not shared among GL contexts)
+  // The renderer would actually work without any VAO bound, but then our VertexAttrib calls would overwrite the default one currently bound.
+  var vertex_array_object : c.GLuint = 0;
+  if (!@hasField(c, "IMGUI_IMPL_OPENGL_ES2"))
+    c.glGenVertexArrays(1, &vertex_array_object);
+  defer if (!@hasField(c, "IMGUI_IMPL_OPENGL_ES2"))
+    c.glDeleteVertexArrays(1, &vertex_array_object);
+
+  SetupRenderState(draw_data, fb_width, fb_height, vertex_array_object);
+
+  // Will project scissor/clipping rectangles into framebuffer space
+  const clip_off = draw_data.*.DisplayPos; // (0,0) unless using multi-viewports
+  const clip_scale = draw_data.*.FramebufferScale; // (1,1) unless using retina display which are often (2,2)
+
+  // Render command lists
+  var n : usize = 0;
+  while (n < @intCast(usize, draw_data.*.CmdListsCount)) : (n += 1) {
+    const cmd_list = draw_data.*.CmdLists[n];
+
+    // Upload vertex/index buffers
+    c.glBufferData(c.GL_ARRAY_BUFFER, cmd_list.*.VtxBuffer.Size * @sizeOf(c.ImDrawVert), @ptrCast(?*c.GLvoid, cmd_list.*.VtxBuffer.Data), c.GL_STREAM_DRAW);
+    c.glBufferData(c.GL_ELEMENT_ARRAY_BUFFER, cmd_list.*.IdxBuffer.Size * @sizeOf(c.ImDrawIdx), @ptrCast(*c.GLvoid, cmd_list.*.IdxBuffer.Data), c.GL_STREAM_DRAW);
+
+    var cmd_i : usize = 0;
+    while (cmd_i < @intCast(usize, cmd_list.*.CmdBuffer.Size)) : (cmd_i += 1) {
+      const pcmd = &cmd_list.*.CmdBuffer.Data[cmd_i];
+
+      if (pcmd.*.UserCallback != null) {
+        // User callback, registered via ImDrawList::AddCallback()
+        // (ImDrawCallback_ResetRenderState is a special callback value used by the user to request the renderer to reset render state.)
+        const ImDrawCallback_ResetRenderState = @intToPtr(c.ImDrawCallback, math.maxInt(usize));
+        if (pcmd.*.UserCallback == ImDrawCallback_ResetRenderState) {
+          SetupRenderState(draw_data, fb_width, fb_height, vertex_array_object);
+        } else {
+          if (pcmd.*.UserCallback) |callback| {
+            callback(cmd_list, pcmd);
+          } else {
+            unreachable;
+          }
+        }
+      } else {
+        // Project scissor/clipping rectangles into framebuffer space
+        var clip_rect : c.ImVec4 = undefined;
+        clip_rect.x = (pcmd.*.ClipRect.x - clip_off.x) * clip_scale.x;
+        clip_rect.y = (pcmd.*.ClipRect.y - clip_off.y) * clip_scale.y;
+        clip_rect.z = (pcmd.*.ClipRect.z - clip_off.x) * clip_scale.x;
+        clip_rect.w = (pcmd.*.ClipRect.w - clip_off.y) * clip_scale.y;
+
+        if (clip_rect.x < @intToFloat(f32, fb_width) and clip_rect.y < @intToFloat(f32, fb_height)
+            and clip_rect.z >= 0.0 and clip_rect.w >= 0.0) {
+          // Apply scissor/clipping rectangle
+          if (clip_origin_lower_left) {
+            c.glScissor(@floatToInt(c.GLint, clip_rect.x), fb_height - @floatToInt(c.GLint, clip_rect.w),
+                        @floatToInt(c.GLint, clip_rect.z - clip_rect.x), @floatToInt(c.GLint, clip_rect.w - clip_rect.y));
+          } else {
+            // Support for GL 4.5 rarely used glClipControl(GL_UPPER_LEFT)
+            c.glScissor(@floatToInt(c.GLint, clip_rect.x), @floatToInt(c.GLint, clip_rect.y),
+                        @floatToInt(c.GLint, clip_rect.z), @floatToInt(c.GLint, clip_rect.w));
+          }
+
+          // Bind texture, Draw
+          c.glBindTexture(c.GL_TEXTURE_2D, @intCast(c.GLuint, @ptrToInt(pcmd.*.TextureId)));
+          const drawIndexSize = @sizeOf(c.ImDrawIdx);
+          const drawIndexType = if (drawIndexSize == 2) c.GL_UNSIGNED_SHORT else c.GL_UNSIGNED_INT;
+          const offset = @intToPtr(?*c.GLvoid, pcmd.*.IdxOffset * drawIndexSize);
+          if (@hasField(c, "IMGUI_IMPL_OPENGL_HAS_DRAW_WITH_BASE_VERTEX")) {
+            c.glDrawElementsBaseVertex(c.GL_TRIANGLES, @intCast(c.GLsizei, pcmd.*.ElemCount), drawIndexType, offset, @intCast(c.GLint, pcmd.*.VtxOffset));
+          } else {
+            c.glDrawElements(c.GL_TRIANGLES, @intCast(c.GLsizei, pcmd.*.ElemCount), drawIndexType, offset);
+          }
+        }
+      }
+    }
+  }
+}
+
+fn SetupRenderState(draw_data: *c.ImDrawData, fb_width: i32, fb_height: i32, vertex_array_object: c.GLuint) void {
+  // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
+  c.glEnable(c.GL_BLEND);
+  c.glBlendEquation(c.GL_FUNC_ADD);
+  c.glBlendFunc(c.GL_SRC_ALPHA, c.GL_ONE_MINUS_SRC_ALPHA);
+  c.glDisable(c.GL_CULL_FACE);
+  c.glDisable(c.GL_DEPTH_TEST);
+  c.glEnable(c.GL_SCISSOR_TEST);
+  if (@hasField(c, "GL_POLYGON_MODE"))
+    c.glPolygonMode(c.GL_FRONT_AND_BACK, c.GL_FILL);
+
+  // Setup viewport, orthographic projection matrix
+  // Our visible imgui space lies from draw_data.*.DisplayPos (top left) to draw_data.*.DisplayPos+data_data.*.DisplaySize (bottom right). DisplayPos is (0,0) for single viewport apps.
+  c.glViewport(0, 0, @intCast(c.GLsizei, fb_width), @intCast(c.GLsizei, fb_height));
+  const L = draw_data.*.DisplayPos.x;
+  const R = draw_data.*.DisplayPos.x + draw_data.*.DisplaySize.x;
+  const T = draw_data.*.DisplayPos.y;
+  const B = draw_data.*.DisplayPos.y + draw_data.*.DisplaySize.y;
+  const ortho_projection = [4][4]f32{
+    [_]f32{ 2.0/(R-L),   0.0,          0.0,   0.0 },
+    [_]f32{ 0.0,         2.0/(T-B),    0.0,   0.0 },
+    [_]f32{ 0.0,         0.0,         -1.0,   0.0 },
+    [_]f32{ (R+L)/(L-R), (T+B)/(B-T),  0.0,   1.0 },
+  };
+  c.glUniform1i(g_AttribLocationTex, 0);
+  c.glUniformMatrix4fv(g_AttribLocationProjMtx, 1, c.GL_FALSE, &ortho_projection[0][0]);
+  if (@hasField(c, "GL_SAMPLER_BINDING"))
+    c.glBindSampler(0, 0); // We use combined texture/sampler state. Applications using GL 3.3 may set that otherwise.
+
+  if (!@hasField(c, "IMGUI_IMPL_OPENGL_ES2"))
+    c.glBindVertexArray(vertex_array_object);
+
+  // Bind vertex/index buffers and setup attributes for ImDrawVert
+  c.glBindBuffer(c.GL_ARRAY_BUFFER, g_VboHandle);
+  c.glBindBuffer(c.GL_ELEMENT_ARRAY_BUFFER, g_ElementsHandle);
+  c.glEnableVertexAttribArray(@intCast(c.GLuint, g_AttribLocationVtxPos));
+  c.glEnableVertexAttribArray(@intCast(c.GLuint, g_AttribLocationVtxUV));
+  c.glEnableVertexAttribArray(@intCast(c.GLuint, g_AttribLocationVtxColor));
+  c.glVertexAttribPointer(@intCast(c.GLuint, g_AttribLocationVtxPos),   2, c.GL_FLOAT,         c.GL_FALSE, @sizeOf(c.ImDrawVert), @intToPtr(?*c.GLvoid, @byteOffsetOf(c.ImDrawVert, "pos")));
+  c.glVertexAttribPointer(@intCast(c.GLuint, g_AttribLocationVtxUV),    2, c.GL_FLOAT,         c.GL_FALSE, @sizeOf(c.ImDrawVert), @intToPtr(?*c.GLvoid, @byteOffsetOf(c.ImDrawVert, "uv")));
+  c.glVertexAttribPointer(@intCast(c.GLuint, g_AttribLocationVtxColor), 4, c.GL_UNSIGNED_BYTE, c.GL_TRUE,  @sizeOf(c.ImDrawVert), @intToPtr(?*c.GLvoid, @byteOffsetOf(c.ImDrawVert, "col")));
+}