From 21689b45f8d7e28bd6be565758bec0205abb8416 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 31 Mar 2013 15:55:29 +0200
Subject: [PATCH 1/1] add options to conrol presentation and clear behaviour

---
 gltest.cpp | 78 ++++++++++++++++++++++++++++--------------------------
 1 file changed, 41 insertions(+), 37 deletions(-)

diff --git a/gltest.cpp b/gltest.cpp
index 8d296a3..0cae932 100644
--- a/gltest.cpp
+++ b/gltest.cpp
@@ -15,13 +15,13 @@ namespace po = boost::program_options;
 #include "glwindow.h"
 #if defined(USE_GLX)
 #include "glxbackend.h"
-GLBackend *createGLBackend()
+static GLBackend *createGLBackend()
 {
 	return new GLXBackend();
 }
 #elif defined(USE_EGL)
 #include "eglbackend.h"
-GLBackend *createGLBackend()
+static GLBackend *createGLBackend()
 {
 	return new EGLBackend();
 }
@@ -30,12 +30,12 @@ GLBackend *createGLBackend()
 #endif
 
 // configuration
-const GLfloat boxWidth = 0.045f;
-const GLfloat boxSpeed = 1.25f; // per second
+static const GLfloat boxWidth = 0.045f;
+static const GLfloat boxSpeed = 1.25f; // per second
 
 // profiler
-const int numProfilerStates = 5;
-const char *profilerStateNames[numProfilerStates] = { "Pre-Render", "Drawing", "Swapping", "Post-Render", "Outside renderer"};
+enum ProfilerState { statePreRender, stateDraw, statePresent, statePostRender, stateOutsideRender, numProfilerStates };
+static const char *profilerStateNames[numProfilerStates] = { "Pre-Render", "Drawing", "Presenting", "Post-Render", "Outside renderer"};
 
 // utility functions
 static double getTime()
@@ -53,7 +53,7 @@ static void drawRect(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2)
 // the window
 class TearTestWindow : public GLWindow {
 public:
-	TearTestWindow() : GLWindow(XOpenDisplay(0), createGLBackend()), boxPos(0), boxDirection(1)
+	TearTestWindow(bool overdraw, bool copy) : GLWindow(XOpenDisplay(0), createGLBackend()), overdraw(overdraw), copy(copy), boxPos(0), boxDirection(1)
 	{}
 
 	void setSwapInterval(int i) {
@@ -89,7 +89,7 @@ protected:
 		glFlush();
 	}
 	
-	void profilerTick(int nextState)
+	void profilerTick(ProfilerState nextState)
 	{
 		assert (nextState >= 0 && nextState < numProfilerStates);
 		double time = getTime();
@@ -113,8 +113,9 @@ protected:
 	}
 	
 	void renderGL()
-	{                            
-		profilerTick(0);
+	{              
+		//////////////////////////////////////////////
+		profilerTick(statePreRender);
 		double time = getTime();
 		// anim
 		double passedTime = time-lastFrame;
@@ -130,37 +131,37 @@ protected:
 			}
 		}
 		lastFrame = time;
-		// draw
-		//glFlush();
-		profilerTick(1);
-		//glClear(GL_COLOR_BUFFER_BIT);
-		glBegin(GL_QUADS);
-		// clear manually
-		glColor3f(0.0f, 0.0f, 0.0f);
-		drawRect(0, 0, 1, 1);
+		//////////////////////////////////////////////
+		profilerTick(stateDraw);
+		if (overdraw) {
+			glBegin(GL_QUADS);
+			// clear manually
+			glColor3f(0.0f, 0.0f, 0.0f);
+			drawRect(0, 0, 1, 1);
+		}
+		else {
+			glClear(GL_COLOR_BUFFER_BIT);
+			glBegin(GL_QUADS);
+		}
 		glColor3f(0.8f, 1.0f, 0.75f);
 		drawRect(boxPos, 0, boxPos+boxWidth, 1);
 		glEnd();
-		usleep(20*1000);
-		profilerTick(2);
-		getBackend()->swapBuffers();
-// 		glDrawBuffer(GL_FRONT);
-// 		int xpos = 0;
-// 		int ypos = 0;
-		//foreach (const QRect &r, region.rects()) {
-			// convert to OpenGL coordinates
-			//int y = displayHeight() - 0 - r.height();
-// 			glBitmap(0, 0, 0, 0, 0 - xpos, 0 - ypos, NULL); // not glRasterPos2f, see glxbackend.cpp
-// 			xpos = 0;
-// 			ypos = 0;
-// 			glCopyPixels(0, 0, getWidth(), getHeight(), GL_COLOR);
-		//}
-// 		glBitmap(0, 0, 0, 0, -xpos, -ypos, NULL); // move position back to 0,0
-// 		glDrawBuffer(GL_BACK);
-		profilerTick(3);
+		//////////////////////////////////////////////
+		profilerTick(statePresent);
+		if (copy) {
+			glDrawBuffer(GL_FRONT);
+			glCopyPixels(0, 0, getWidth(), getHeight(), GL_COLOR);
+			glDrawBuffer(GL_BACK);
+		}
+		else {
+			getBackend()->swapBuffers();
+		}
+		//////////////////////////////////////////////
+		profilerTick(statePostRender);
 		glFlush();
 		++framect;
-		profilerTick(4);
+		//////////////////////////////////////////////
+		profilerTick(stateOutsideRender);
 	}
 	
 	virtual void handleKeyPress(KeySym key)
@@ -173,6 +174,7 @@ protected:
 	}
 
 private:
+	bool overdraw, copy;
 	double lastFrame;
 	GLfloat boxPos, boxDirection;
 	// FPS
@@ -190,6 +192,8 @@ int main(int argc, char ** argv)
 	desc.add_options()
 		("help,h", "produce help message")
 		("swap-interval,i", po::value<int>(), "set swap interval")
+		("copy,c", "copy to front buffer (instead of performing a buffer swap)")
+		("overdraw,o", "overdraw previous image (instead of calling glClear)")
 	;
 	po::variables_map vm;
 	po::store(po::parse_command_line(argc, argv, desc), vm);
@@ -201,7 +205,7 @@ int main(int argc, char ** argv)
 	}
 
 	// actual program
-	TearTestWindow w;
+	TearTestWindow w(vm.count("overdraw"), vm.count("copy"));
 	w.open(800, 600);
 	if (vm.count("swap-interval"))
 		w.setSwapInterval(vm["swap-interval"].as<int>());
-- 
2.30.2