Refactor the renderer frame flush functionality.

This commit does three things:
  * Recognizes that BeginFrame()/EndFrame() are badly named, since
    BeginFrame() sets up framebuffer, and EndFrame() flushes a frame,
    and they do not have to be called in pairs; and so renames them
    to NewFrame()/FlushFrame().
  * Reduces the amount of frame flushes in GraphicsWindow::Paint()
    to two, which is the minimum since we use two different cameras
    for geometry and UI;
  * Changes the FPS measurement code to only take into account
    the time spent rendering our main geometry, and not the UI
    rendering or window system interaction time.

src/draw.cpp

@@ -751,8 +751,6 @@ void GraphicsWindow::Paint() {
 
     havePainted = true;
 
-    auto renderStartTime = std::chrono::high_resolution_clock::now();
-
     int w, h;
     GetGraphicsWindowSize(&w, &h);
     width = w;
@@ -772,13 +770,20 @@ void GraphicsWindow::Paint() {
         ForceTextWindowShown();
     }
 
-    canvas->BeginFrame();
+    auto renderStartTime = std::chrono::high_resolution_clock::now();
+
+    canvas->NewFrame();
     canvas->SetCamera(camera);
     canvas->SetLighting(lighting);
     Draw(canvas.get());
-    canvas->EndFrame();
+    canvas->FlushFrame();
+
+    auto renderEndTime = std::chrono::high_resolution_clock::now();
+    std::chrono::duration<double, std::milli> renderTime = renderEndTime - renderStartTime;
 
     camera.LoadIdentity();
+    camera.offset.x = -(double)camera.width  / 2.0;
+    camera.offset.y = -(double)camera.height / 2.0;
     canvas->SetCamera(camera);
 
     UiCanvas uiCanvas = {};
@@ -788,29 +793,22 @@ void GraphicsWindow::Paint() {
     // rectangle, as an outline and a transparent fill.
     if(pending.operation == Pending::DRAGGING_MARQUEE) {
         Point2d begin = ProjectPoint(orig.marqueePoint);
-        uiCanvas.DrawRect((int)orig.mouse.x, (int)begin.x,
-                          (int)orig.mouse.y, (int)begin.y,
+        uiCanvas.DrawRect((int)orig.mouse.x + (int)camera.width / 2,
+                          (int)begin.x + (int)camera.width / 2,
+                          (int)orig.mouse.y + (int)camera.height / 2,
+                          (int)begin.y + (int)camera.height / 2,
                           /*fillColor=*/Style::Color(Style::HOVERED).WithAlpha(25),
                           /*outlineColor=*/Style::Color(Style::HOVERED));
-        canvas->EndFrame();
     }
 
     // And finally the toolbar.
     if(SS.showToolbar) {
-        camera.offset   = {};
-        camera.offset.x = -(double)camera.width  / 2.0;
-        camera.offset.y = -(double)camera.height / 2.0;
         canvas->SetCamera(camera);
         ToolbarDraw(&uiCanvas);
     }
 
     // If we display UI elements, also display an fps counter.
     if(SS.showToolbar) {
-        canvas->EndFrame();
-
-        auto renderEndTime = std::chrono::high_resolution_clock::now();
-        std::chrono::duration<double, std::milli> renderTime = renderEndTime - renderStartTime;
-
         RgbaColor renderTimeColor;
         if(1000 / renderTime.count() < 60) {
             // We aim for a steady 60fps; draw the counter in red when we're slower.
@@ -824,6 +822,6 @@ void GraphicsWindow::Paint() {
                                 5, 5, renderTimeColor);
     }
 
-    canvas->EndFrame();
+    canvas->FlushFrame();
     canvas->Clear();
 }

src/render/render.h

@@ -175,8 +175,8 @@ public:
     virtual void SetCamera(const Camera &camera, bool filp = FLIP_FRAMEBUFFER) = 0;
     virtual void SetLighting(const Lighting &lighting) = 0;
 
-    virtual void BeginFrame() = 0;
-    virtual void EndFrame() = 0;
+    virtual void NewFrame() = 0;
+    virtual void FlushFrame() = 0;
     virtual std::shared_ptr<Pixmap> ReadFrame() = 0;
 
     virtual void GetIdent(const char **vendor, const char **renderer, const char **version) = 0;

src/render/rendergl1.cpp

@@ -220,8 +220,8 @@ public:
     void SetCamera(const Camera &camera, bool filp = FLIP_FRAMEBUFFER) override;
     void SetLighting(const Lighting &lighting) override;
 
-    void BeginFrame() override;
-    void EndFrame() override;
+    void NewFrame() override;
+    void FlushFrame() override;
     std::shared_ptr<Pixmap> ReadFrame() override;
 
     void GetIdent(const char **vendor, const char **renderer, const char **version) override;
@@ -738,7 +738,7 @@ void OpenGl1Renderer::UpdateProjection(bool flip) {
     glClear(GL_DEPTH_BUFFER_BIT);
 }
 
-void OpenGl1Renderer::BeginFrame() {
+void OpenGl1Renderer::NewFrame() {
     glEnable(GL_NORMALIZE);
 
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
@@ -791,7 +791,7 @@ void OpenGl1Renderer::BeginFrame() {
     glClear(GL_DEPTH_BUFFER_BIT);
 }
 
-void OpenGl1Renderer::EndFrame() {
+void OpenGl1Renderer::FlushFrame() {
     UnSelectPrimitive();
     glFlush();
 

src/render/rendergl2.cpp

@@ -134,8 +134,8 @@ public:
     void SetCamera(const Camera &c, bool flip) override;
     void SetLighting(const Lighting &l) override;
 
-    void BeginFrame() override;
-    void EndFrame() override;
+    void NewFrame() override;
+    void FlushFrame() override;
     std::shared_ptr<Pixmap> ReadFrame() override;
 
     void GetIdent(const char **vendor, const char **renderer, const char **version) override;
@@ -611,7 +611,7 @@ void OpenGl2Renderer::UpdateProjection(bool flip) {
     glClear(GL_DEPTH_BUFFER_BIT);
 }
 
-void OpenGl2Renderer::BeginFrame() {
+void OpenGl2Renderer::NewFrame() {
     if(!initialized) {
         Init();
         initialized = true;
@@ -632,7 +632,7 @@ void OpenGl2Renderer::BeginFrame() {
     glPolygonOffset(2.0, 1.0);
 }
 
-void OpenGl2Renderer::EndFrame() {
+void OpenGl2Renderer::FlushFrame() {
     for(SMeshListItem &li : meshes) {
         Fill *fill = SelectFill(li.h);
 

src/textwin.cpp

@@ -865,7 +865,7 @@ void TextWindow::Paint() {
     camera.offset.x = -(double)camera.width  / 2.0;
     camera.offset.y = -(double)camera.height / 2.0;
 
-    canvas->BeginFrame();
+    canvas->NewFrame();
     canvas->SetCamera(camera);
 
     UiCanvas uiCanvas = {};
@@ -992,7 +992,7 @@ void TextWindow::Paint() {
     // And we may show a color picker for certain editable fields
     DrawOrHitTestColorPicker(&uiCanvas, PAINT, false, 0, 0);
 
-    canvas->EndFrame();
+    canvas->FlushFrame();
     canvas->Clear();
 }