关于我的代码我有两个问题; 1.为什么我在glutDisplayFunc，2上收到此错误'glutDisplayFunc' : cannot convert parameter 1 from 'void (__cdecl *)(float [],float [],int,int [],int [],float [],float [],float [],float,float,float,float,float)' to 'void (__cdecl *)(void)'
1> None of the functions with this name in scope match the target type。为什么我在整个案例陈述中的i上都会出现初始化和声明错误？我相信我的代码顺序正确，但老实说这是我第一次将所有这些方面都放在一个功能中。
我不确定你需要哪些代码来指导我正确的方向，所以我发布了所有...
void init(void); //function that initializes the window clear color
void DrawsAllIcons(float x[], float y[], int ndraws, int pointsperdraw [], int drawtype[], float colorr[], float colorg[], float colorb[], float rotate, float scalex, float scaley, float transx, float transy); //function to draw the functions in the opened window
void SetupRC(void);
void RenderScene(void);
void settrans2 (float rotate, float scalex, float scaley, float transx, float transy);//function that sets the clear color used to set the state of the OpenGL system
int main(int argc, char* *argv)
{
char header[]="This Bad Boy'll Draw any Icon you can think of"; //set up window title
glutInit(&argc, argv); // initialize glopen utility toolkit
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGBA); // Set up the display mode with a buffer and colors
glutInitWindowSize(900,650); //Initialize window size and position
glutInitWindowPosition(0,0);
glutCreateWindow(header); // Open and label the window
glutDisplayFunc(RenderScene); //points to the fucntion that will be drawing the item
SetupRC(); // Set the state of the rendering machine
glutMainLoop(); // Call and activate the main
return 0;
}
void RenderScene(void)
{
glClear(GL_COLOR_BUFFER_BIT);//note clear color was set in SetupRC
glLoadIdentity();
glViewport(25,25,900,500); //set the viewport to the window dimensions
glOrtho(-7.0,7.0,-30.0,50.0,1.0,-1.0);
float xCoords [7] = {1.0, 1.0, -1.0, -1.0, 1.0, 0.0, 0.0};
float yCoords [7] = {1.0,-1.0,-1.0,1.0,1.0,2.0,-2.0};
int numberofDraws = 2;
int pointsPerDraw[2] = {5, 2};
int typeOfDraw[2] = {2,1};
float colorR[3] = {1.0,0.0,0.0};
float colorg[3] = {0.0,1.0,0.0};
float colorb[3] = {0.0,0.0,1.0};
float rotate = 30.0;
float transx = 3.0;
float transy = 3.0;
float scalex = 1.0;
float scaley = 1.0;
DrawsAllIcons(xCoords, yCoords, numberofDraws, pointsPerDraw,typeOfDraw,colorR,colorg,colorb, rotate, transx,transy,scalex,scaley);
}
void DrawsAllIcons (float x[], float y[], int ndraws, int pointsperdraw [], int drawtype[], float colorr[], float colorg[], float colorb[], float rotate, float scalex, float scaley, float transx, float transy)
{
int k=0; //index for arrays
int drawTooIndex = 0;
for (int j=0; j<=ndraws; j++) //runs through
{
int whatCase = drawtype[j]; //sees what type of draw
drawTooIndex +=pointsperdraw[j];
switch (whatCase)
{
case 1:
{
glColor3f(colorr[j],colorg[j],colorb[j]);
settrans2(rotate,scalex,scaley,transx,transy); // is this where it needs to be?
glBegin(GL_LINES);
glVertex2f(x[k], y[k]); //sets vertex at the first point at k in the point arrays
int i = k+1;
k++;
for (i; i <drawTooIndex; i++) //pointsperdraw[k] needs messed with maybe?
{
glVertex2f(x[i], y[i]);
k++;
}
glEnd();
glFlush();
}
break;
case 2:
{
glColor3f(colorr[j], colorg[j], colorb[j]);
settrans2(rotate,scalex,scaley,transx,transy);
glBegin(GL_LINE_STRIP);
glVertex2f(x[k], y[k]);
int m = k+1;
k++;
for (m; m <drawTooIndex; m++)
{
glVertex2f(x[m], y[m]);
k++;
}
glEnd();
glFlush();
}
break;
case 3:
{
glColor3f(colorr[j], colorg[j], colorb[j]);
settrans2(rotate,scalex,scaley,transx,transy);
glShadeModel(GL_FLAT);
glBegin(GL_POLYGON);
glVertex2f(x[k], y[k]);
int n = k+1; //gets index of where to start drawing in the x and y arrays
k++;
for (n; n <drawTooIndex; n++)
{
glVertex2f(x[n], y[n]);
k++;
}
glEnd();
glFlush();
}
break;
}
}
}
void SetupRC(void)
{ // function sets the clear color of an open window, and then clears the open window
glClearColor(0.560784f, 0.737255f, 0.560784f, 1.0f); // Set clear color to pale green
return;
}//end of SetupRC
void settrans2(float rotate, float scalex, float scaley, float transx, float transy)
{
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(transx,transy,0.0);
glRotatef(rotate, 0.0, 0.0, 1.0); // where to put this in the program?
glScalef(scalex, scaley, 1.0);
return;
}
答案 0 :(得分：1)
这与基本的C ++有很大关系，而不是OpenGL。
关于第一个问题：glutDisplayFunc()的参数是一个函数指针。传递的值的类型需要与函数参数的类型匹配。查看documentation，声明是：
void glutDisplayFunc(void (*func)(void));
因此，参数是一个指向函数的指针，该函数具有返回类型void，并且没有参数。您正在尝试传递具有参数的函数，该函数与声明不匹配。这几乎是编译器告诉你的。
还有另一个合理的理由说明为什么你要做的事情不可能奏效。只要需要重绘，GLUT就会调用您传递给glutDisplayFunc()的函数。如果它必须调用你的DrawAllIcons()函数，它将如何知道为其参数传递的值？它真的不能。
关于case语句中定义的变量：定义switch语句的方式，每个case 不开始新范围。哪种有意义，因为每个case内的代码都没有被通常指定新范围的花括号所包围。这意味着整个switch语句中的所有内容都形成一个范围。
由于控制逻辑可以跳过此范围内的部分代码，因此可能会遇到奇怪的情况，即跳过变量的定义（可能包括初始化），但之后会在没有定义的情况下使用内部执行的代码。例如：
switch (...)
{
case 1:
...
int foo = 7;
...
break;
case 2:
...
int bar = foo;
...
break;
}
如果选择案例2，foo的价值是多少？我们跳过了初始化。它是否存在，因为我们跳过了定义？嗯，确实如此，因为它早先在同一范围内宣布。另一方面，我们从未执行过包含定义的代码。
为了避免这些真正没有答案的问题，C ++根本不允许在case语句中直接使用变量定义。
如果您想在case语句中使用局部变量，则始终可以通过启动新块来创建新范围。在上面：
switch (...)
{
case 1:
{
...
int foo = 7;
...
}
break;
case 2:
{
...
int bar = foo;
...
}
break;
}
现在每个case都有一个范围，它允许定义局部变量，并且很清楚它们的范围开始的位置和结束位置。