Add defaultCanvas;

Having a normal Canvas object that represents the backbuffer reduces
some indirection where we have to last-minute check if a Canvas is
set.  It also means that all of the draw-related info that was _sometimes_
on the Canvas is now _always_ on the Canvas, which reduces the amount
of redundant information we need to provide for a draw call.

There may be some issues related to changing the width/height/stereo
of the default Canvas.

src/modules/graphics/graphics.c

@@ -94,6 +94,7 @@ static struct {
   int width;
   int height;
   Camera camera;
+  Canvas* defaultCanvas;
   Shader* defaultShaders[MAX_DEFAULT_SHADERS];
   Material* defaultMaterial;
   Font* defaultFont;
@@ -158,6 +159,8 @@ static void onCloseWindow(void) {
 static void onResizeWindow(int width, int height) {
   state.width = width;
   state.height = height;
+  state.defaultCanvas->width = width;
+  state.defaultCanvas->height = height;
 }
 
 static void* lovrGraphicsMapBuffer(StreamType type, uint32_t count) {
@@ -194,6 +197,7 @@ void lovrGraphicsDestroy() {
   lovrRelease(Buffer, state.identityBuffer);
   lovrRelease(Material, state.defaultMaterial);
   lovrRelease(Font, state.defaultFont);
+  lovrRelease(Canvas, state.defaultCanvas);
   lovrGpuDestroy();
   memset(&state, 0, sizeof(state));
 }
@@ -212,6 +216,8 @@ void lovrGraphicsCreateWindow(WindowFlags* flags) {
   lovrPlatformGetFramebufferSize(&state.width, &state.height);
   lovrGpuInit(lovrGetProcAddress);
 
+  state.defaultCanvas = lovrCanvasCreateFromHandle(state.width, state.height, (CanvasFlags) { .stereo = false }, 0, 0, 0, 1, true);
+
   for (int i = 0; i < MAX_STREAMS; i++) {
     state.buffers[i] = lovrBufferCreate(bufferCount[i] * bufferStride[i], NULL, bufferType[i], USAGE_STREAM, false);
   }
@@ -281,8 +287,15 @@ void lovrGraphicsSetCamera(Camera* camera, bool clear) {
     mat4_identity(state.camera.viewMatrix[1]);
     mat4_perspective(state.camera.projection[0], .01f, 100.f, 67.f * (float) M_PI / 180.f, (float) state.width / state.height);
     mat4_perspective(state.camera.projection[1], .01f, 100.f, 67.f * (float) M_PI / 180.f, (float) state.width / state.height);
+    state.camera.canvas = state.defaultCanvas;
+    state.camera.canvas->flags.stereo = false;
   } else {
     state.camera = *camera;
+
+    if (!state.camera.canvas) {
+      state.camera.canvas = state.defaultCanvas;
+      state.camera.canvas->flags.stereo = camera->stereo;
+    }
   }
 
   if (clear) {
@@ -724,10 +737,7 @@ void lovrGraphicsFlush() {
       .drawMode = batch->drawMode,
       .instances = instances,
       .rangeStart = rangeStart,
-      .rangeCount = rangeCount,
-      .width = batch->canvas ? lovrCanvasGetWidth(batch->canvas) : state.width,
-      .height = batch->canvas ? lovrCanvasGetHeight(batch->canvas) : state.height,
-      .stereo = batch->canvas ? lovrCanvasIsStereo(batch->canvas) : state.camera.stereo
+      .rangeCount = rangeCount
     });
   }
 }

src/modules/graphics/graphics.h

@@ -215,9 +215,6 @@ typedef struct {
   uint32_t instances;
   uint32_t rangeStart;
   uint32_t rangeCount;
-  uint32_t width : 15;
-  uint32_t height : 15;
-  bool stereo : 1;
 } DrawCommand;
 
 void lovrGpuInit(getProcAddressProc getProcAddress);

src/modules/graphics/opengl.c

@@ -614,14 +614,14 @@ static void lovrGpuBindMesh(Mesh* mesh, Shader* shader, int baseDivisor) {
 }
 
 static void lovrGpuBindCanvas(Canvas* canvas, bool willDraw) {
-  if (canvas) {
-    lovrGpuBindFramebuffer(canvas->framebuffer);
-    canvas->needsResolve = willDraw;
-  } else {
-    lovrGpuBindFramebuffer(0);
+  lovrGpuBindFramebuffer(canvas->framebuffer);
+
+  if (canvas->framebuffer == 0) {
     return;
   }
 
+  canvas->needsResolve = willDraw;
+
   if (!canvas->needsAttach) {
     return;
   }
@@ -1135,7 +1135,7 @@ void lovrGpuDiscard(Canvas* canvas, bool color, bool depth, bool stencil) {
   int count = 0;
 
   if (color) {
-    int n = canvas ? canvas->attachmentCount : 1;
+    int n = MAX(canvas->attachmentCount, 1);
     for (int i = 0; i < n; i++) {
       attachments[count++] = GL_COLOR_ATTACHMENT0 + i;
     }
@@ -1155,14 +1155,14 @@ void lovrGpuDiscard(Canvas* canvas, bool color, bool depth, bool stencil) {
 
 void lovrGpuDraw(DrawCommand* draw) {
   lovrAssert(state.singlepass != MULTIVIEW || draw->shader->multiview == draw->canvas->flags.stereo, "Shader and Canvas multiview settings must match!");
-  uint32_t viewportCount = (draw->stereo && state.singlepass != MULTIVIEW) ? 2 : 1;
+  uint32_t viewportCount = (draw->canvas->flags.stereo && state.singlepass != MULTIVIEW) ? 2 : 1;
   uint32_t drawCount = state.singlepass == NONE ? viewportCount : 1;
   uint32_t instanceMultiplier = state.singlepass == INSTANCED_STEREO ? viewportCount : 1;
   uint32_t viewportsPerDraw = instanceMultiplier;
   uint32_t instances = MAX(draw->instances, 1) * instanceMultiplier;
 
-  float w = state.singlepass == MULTIVIEW ? draw->width : draw->width / (float) viewportCount;
-  float h = draw->height;
+  float w = state.singlepass == MULTIVIEW ? draw->canvas->width : draw->canvas->width / (float) viewportCount;
+  float h = draw->canvas->height;
   float viewports[2][4] = { { 0.f, 0.f, w, h }, { w, 0.f, w, h } };
   lovrShaderSetInts(draw->shader, "lovrViewportCount", &(int) { viewportCount }, 0, 1);