Question

opengl 里 state==GLUT_DOWN 这句是什么意思？？

if(button == GLUT_LEFT_BUTTON)
{
if(state == GLUT_DOWN)
{ mousedown = true; loopr = false;}
else
mousedown=false;
}
if (button== GLUT_RIGHT_BUTTON)
{if(state == GLUT_DOWN)
loopr=true; glutTimerFunc(200,timer,0);

上下文

Answer 1

if(state == GLUT_DOWN) //callback was due to a press (of a mouse button)
//相当于“如果某个鼠标键被按下”
if(state == GLUT_UP) //callback was due to a release (of a mouse button)
//相当于“如果某个鼠标键被放开（弹起）”
if (button== GLUT_LEFT_BUTTON) //callback was due to a release/press of the LEFT button
//相当于“如果鼠标左键被按下或者被放开”
if (button== GLUT_RIGHT_BUTTON) //callback was due to a release/press of the RIGHT button
//相当于“如果鼠标右键被按下或者被放开”
if (button== GLUT_MIDDLE_BUTTON) //callback was due to a release/press of the MIDDLE
//button
//相当于“如果鼠标中键被按下或者被放开”

因此，
if(button == GLUT_LEFT_BUTTON)
{
if(state == GLUT_DOWN)
……
//相当于“如果鼠标左键被按下”

if(button == GLUT_RIGHT_BUTTON)
{
if(state == GLUT_DOWN)
……
//相当于“如果鼠标右键被按下”

Answer 2

这是glut里定义的一个量，表示鼠标左键被按下