OpenGL Programming Guide- Red Book 例子程序库 -系列- 2-Introduction to OpenGL-Part2

Example 1-3 : A Double-Buffered Program: double.c

原始程序

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glx.h>
#include "aux.h"

static GLfloat spin = 0.0;

void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
glRotatef(spin, 0.0, 0.0, 1.0);
glRectf(-25.0, -25.0, 25.0, 25.0);
glPopMatrix();

glFlush();
glXSwapBuffers(auxXDisplay(), auxXWindow());
}

void spinDisplay(void)
{
spin = spin + 2.0;
if (spin > 360.0)
spin = spin - 360.0;
display();
}

void startIdleFunc(AUX_EVENTREC *event)
{
auxIdleFunc(spinDisplay);
}

void stopIdleFunc(AUX_EVENTREC *event)
{
auxIdleFunc(0);
}

void myinit(void)
{
glClearColor(0.0, 0.0, 0.0, 1.0);
glColor3f(1.0, 1.0, 1.0);
glShadeModel(GL_FLAT);
}

void myReshape(GLsizei w, GLsizei h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
glOrtho (-50.0, 50.0, -50.0*(GLfloat)h/(GLfloat)w,
50.0*(GLfloat)h/(GLfloat)w, -1.0, 1.0);
else
glOrtho (-50.0*(GLfloat)w/(GLfloat)h,
50.0*(GLfloat)w/(GLfloat)h, -50.0, 50.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity ();
}

int main(int argc, char** argv)
{
auxInitDisplayMode(AUX_DOUBLE | AUX_RGBA);
auxInitPosition(0, 0, 500, 500);
auxInitWindow(argv[0]);
myinit();
auxReshapeFunc(myReshape);
auxIdleFunc(spinDisplay);
auxMouseFunc(AUX_LEFTBUTTON, AUX_MOUSEDOWN, startIdleFunc);
auxMouseFunc(AUX_MIDDLEBUTTON, AUX_MOUSEDOWN, stopIdleFunc);
auxMainLoop(display);
}

和前例一样添加了必要的头文件和lib之后

编译错误__stdcall

--------------------Configuration: Example_1_3 - Win32 Debug--------------------
Compiling...
Example_1_3.cpp
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(31) : warning C4244: '=' : conversion from 'double' to 'float', possible loss of data
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(33) : warning C4244: '=' : conversion from 'double' to 'float', possible loss of data
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(39) : error C2664: 'auxIdleFunc' : cannot convert parameter 1 from 'void (void)' to 'void (__stdcall *)(void)'
None of the functions with this name in scope match the target type
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(76) : error C2664: 'auxReshapeFunc' : cannot convert parameter 1 from 'void (int,int)' to 'void (__stdcall *)(int,int)'
None of the functions with this name in scope match the target type
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(77) : error C2664: 'auxIdleFunc' : cannot convert parameter 1 from 'void (void)' to 'void (__stdcall *)(void)'
None of the functions with this name in scope match the target type
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(78) : error C2664: 'auxMouseFunc' : cannot convert parameter 3 from 'void (struct _AUX_EVENTREC *)' to 'void (__stdcall *)(struct _AUX_EVENTREC *)'
None of the functions with this name in scope match the target type
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(79) : error C2664: 'auxMouseFunc' : cannot convert parameter 3 from 'void (struct _AUX_EVENTREC *)' to 'void (__stdcall *)(struct _AUX_EVENTREC *)'
None of the functions with this name in scope match the target type
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(80) : error C2664: 'auxMainLoop' : cannot convert parameter 1 from 'void (void)' to 'void (__stdcall *)(void)'
None of the functions with this name in scope match the target type
E:\OpenGLRB\Example_1_3\Example_1_3.cpp(81) : warning C4508: 'main' : function should return a value; 'void' return type assumed
Error executing cl.exe.
Creating browse info file...

Example_1_3.exe - 6 error(s), 3 warning(s)

其中的

error C2664: 'auxMainLoop' : cannot convert parameter 1 from 'void (void)' to 'void (__stdcall *)(void)'

该错误处理方案为在各函数前添加__stdcall符号，如下

void __stdcall stopIdleFunc(AUX_EVENTREC *event)
{
auxIdleFunc(0);
}

void __stdcall myinit(void)
{
glClearColor(0.0, 0.0, 0.0, 1.0);
glColor3f(1.0, 1.0, 1.0);
glShadeModel(GL_FLAT);
}

原始代码是在XWindows下面的编写的，转WindowVC，glx.h是无效的，glXSwapBuffers(auxXDisplay(), auxXWindow());函数调用也无效，改为auxSwapBuffers();

调整后cpp文件

// Example_1_3.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "windows.h"
#include <GL/gl.h>
#include <GL/glaux.h>

#pragma comment(lib,"opengl32.lib")
#pragma comment(lib,"glaux.lib")

static GLfloat spin = 0.0;

void __stdcall display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
glRotatef(spin, 0.0, 0.0, 1.0);
glRectf(-25.0, -25.0, 25.0, 25.0);
glPopMatrix();

glFlush();
//glXSwapBuffers(auxXDisplay(), auxXWindow());
auxSwapBuffers();
}

void  __stdcall spinDisplay(void)
{
spin = spin + 2.0;
if (spin > 360.0)
spin = spin - 360.0;
display();
}

void __stdcall startIdleFunc(AUX_EVENTREC *event)
{
auxIdleFunc(spinDisplay);
}

void __stdcall stopIdleFunc(AUX_EVENTREC *event)
{
auxIdleFunc(0);
}

void __stdcall myinit(void)
{
glClearColor(0.0, 0.0, 0.0, 1.0);
glColor3f(1.0, 1.0, 1.0);
glShadeModel(GL_FLAT);
}

void __stdcall myReshape(GLsizei w, GLsizei h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
if (w <= h)
glOrtho (-50.0, 50.0, -50.0*(GLfloat)h/(GLfloat)w,
50.0*(GLfloat)h/(GLfloat)w, -1.0, 1.0);
else
glOrtho (-50.0*(GLfloat)w/(GLfloat)h,
50.0*(GLfloat)w/(GLfloat)h, -50.0, 50.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity ();
}

int main(int argc, char** argv)
{
auxInitDisplayMode(AUX_DOUBLE | AUX_RGBA);
auxInitPosition(0, 0, 500, 500);
auxInitWindow(argv[0]);
myinit();
auxReshapeFunc(myReshape);
auxIdleFunc(spinDisplay);
auxMouseFunc(AUX_LEFTBUTTON, AUX_MOUSEDOWN, startIdleFunc);
auxMouseFunc(AUX_MIDDLEBUTTON, AUX_MOUSEDOWN, stopIdleFunc);
auxMainLoop(display);
return 0;
}

后记：此程序将Example1-1中的代码分散在多个函数中，但是流程顺序保持不变，通过改变参数实现动画效果，鼠标中键单击停止，左键单击启动。

所有aux开头的函数都不重要，所有gl开头的函数都是必须理解掌握的。