macos - glutPassiveMotionFunc和glutWarpMousePointer

我想在OpenGL/GLUT窗口中实现自己的光标。这样做的通常方法是卡住光标(这样光标就不会碰到屏幕的边缘)并自己跟踪其位置。我可以使用来使屏幕上的光标不可见

glutSetCursor(GLUT_CURSOR_NONE);

然后在我的glutPassiveMotionFunc回调内部，使用

int centerX = (float)kWindowWidth / 2.0;
int centerY = (float)kWindowHeight / 2.0;

int deltaX = (x - centerX);
int deltaY = (y - centerY);

mouseX += deltaX / (float)kWindowWidth;
mouseY -= deltaY / (float)kWindowHeight;

glutWarpPointer( centerX, centerY );

这样做的原因是它使指针停留在窗口的中间。问题是，当我绘制“OpenGL”鼠标(在glutDisplayFunc()回调内部)时，它非常生涩。

我在网上查看，发现可能存在一个问题，其中glutWarpPointer()导致再次调用glutPassiveMotionFunc回调，从而导致循环，但这似乎没有发生。

我在Mac OS X上，发现一个帖子说CGDisplayMoveCursorToPoint更适合此操作。调用CGDisplayMoveCursorToPoint可以，但是运动仍然非常不稳定(而且我似乎收到很多x和y均为0的事件)。无论如何，我也希望它也可以在Linux上运行，因此，仅Mac的解决方案不是理想的选择(但是我可以在不同的系统上做不同的事情)。

我已经将其简化为一个测试用例。

#include <stdio.h>
#include <OpenGL/OpenGL.h>
#include <GLUT/GLUT.h>

int curX = 0;
int curY = 0;

void display() {
    glClearColor( 0.0, 0.0, 0.0, 1.0 );
    glClear( GL_COLOR_BUFFER_BIT );

    float vx = (float)curX / 300.0 + 0.5;
    float vy = (float)curY / 300.0 + 0.5;

    glColor3f( 1.0, 0.0, 0.0 );
    glBegin( GL_POINTS );
        glVertex3f( vx, vy, 0.0 );
    glEnd();

    glutSwapBuffers();

}

void passivemotion( int x, int y ) {
    int centerX = 150;
    int centerY = 150;

    int deltaX = x - centerX;
    int deltaY = y - centerY;
    curX += deltaX;
    curY -= deltaY;

    glutWarpPointer( centerX, centerY );
}

void timer( int val ) {
    glutTimerFunc( 16, &timer,  0);
    glutPostRedisplay();
}

int main (int argc, char * argv[]) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB);
    glutInitWindowSize(300,300);
    glutCreateWindow("FPS Mouse Sample");
    glutDisplayFunc(&display);
    glutPassiveMotionFunc(&passivemotion);
    glutSetCursor( GLUT_CURSOR_NONE );
    glutTimerFunc( 16, &timer, 0 );
    glutMainLoop();
    return 0;
}

最佳答案

感谢aib的提示。您让我调查了glutWarpPointer的反汇编，发现发生了什么变得很明显。调用glutWarpPointer CGPostMouseEvent会导致一堆无意义的事件(并且没有任何方法可以跳过它们，因为每帧只获得一次Mouse Events，新的“真实”事件将延迟)。我发现的解决方案是仅在指针位于屏幕边缘时才弯曲(毕竟，该点要装作好像该点永远无法到达屏幕边缘)。无论如何，这是代码。

int lastX = 150;
int lastY = 150;
void passivemotion( int x, int y ) {
    int deltaX = x - lastX;
    int deltaY = y - lastY;

    lastX = x;
    lastY = y;

    if( deltaX == 0 && deltaY == 0 ) return;

    int windowX     = glutGet( GLUT_WINDOW_X );
    int windowY     = glutGet( GLUT_WINDOW_Y );
    int screenWidth     = glutGet( GLUT_SCREEN_WIDTH );
    int screenHeight    = glutGet( GLUT_SCREEN_HEIGHT );

    int screenLeft = -windowX;
    int screenTop = -windowY;
    int screenRight = screenWidth - windowX;
    int screenBottom = screenHeight - windowY;

    if( x <= screenLeft+10 || (y) <= screenTop+10 || x >= screenRight-10 || y >= screenBottom - 10) {
        lastX = 150;
        lastY = 150;
        glutWarpPointer( lastX, lastY );
        //  If on Mac OS X, the following will also work (and CGwarpMouseCursorPosition seems faster than glutWarpPointer).
        //  CGPoint centerPos = CGPointMake( windowX + lastX, windowY + lastY );
        //  CGWarpMouseCursorPosition( centerPos );
        // Have to re-hide if the user touched any UI element with the invisible pointer, like the Dock.
        //  CGDisplayHideCursor(kCGDirectMainDisplay);
    }

    curX += deltaX;
    curY -= deltaY;
}

关于macos - glutPassiveMotionFunc和glutWarpMousePointer，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/728049/