c++ - SDL 在没有焦点时不会停止移动鼠标 - SDL C++

Question

我希望我的游戏引擎停止将鼠标移动到中心(用于偏航和俯仰相机计算)。我写了一些应该处理它的代码，但鼠标在最小化时仍然移动。

void mainLoop()
{
    // This is the main logic portion of the engine
    bool done = false;
    bool visible = true;
    SDL_Event event;

    // Check to make sure we are supposed to quit
    while(! done)
    {
        // Check for SDL events
        while( SDL_PollEvent(& event) )
        {
            // Figure out which event the user has triggered
            switch ( event.type )
            {
                case SDL_QUIT :
                    done = true;
                    break;
                case SDL_ACTIVEEVENT:
                    if( event.active.state & SDL_APPACTIVE )
                    {
                        //If the application is no longer active
                        if(event.active.gain == 0)
                        {
                            visible = false;
                        }
                        else
                        {
                            visible = true;
                        }
                    }
                case SDL_KEYDOWN :

                    // Check for user input
                    switch(event.key.keysym.sym)
                    {
                        // Escape - end the program
                        case SDLK_ESCAPE :
                            done = true;
                            break;
                        // Plus key - increase the speed of the camera
                        case SDLK_PLUS :
                        case SDLK_KP_PLUS :
                            if(camera.walkSpeed < 20.0f) { camera.walkSpeed += 1.0f; }
                            break;
                        // Minus key - decrease the speed of the camera
                        case SDLK_KP_MINUS :
                        case SDLK_MINUS :
                            if(camera.walkSpeed > 2.0f) {camera.walkSpeed -= 1.0f; }
                            break;
                        // F1 - save a TGA screenshot
                        case SDLK_F1:
                            saveScreenshot();
                            break;
                        // All other unassigned keys
                        default:
                            break;
                    }
            }
        }
        // All events have been handled, now handle logic and rendering
        if(visible)
        {
            updateFrame();
            renderFrame();
        }
    }
}

当应用程序失去焦点时，它应该将可见标志设置为 false，从而停止更新和渲染功能。有什么想法吗？

Answer 1

试试这个:

#include <SDL.h>
#include <iostream>

using namespace std;

int main( int argc, char** argv )
{
    SDL_Init( SDL_INIT_EVERYTHING ); 
    SDL_SetVideoMode( 640, 480, 32, SDL_ANYFORMAT );

    bool visible = true;
    bool done = false;
    while( !done )
    {
        SDL_Event event;
        while( SDL_PollEvent(& event) )
        {
            switch ( event.type )
            {
            case SDL_QUIT :
                done = true;
                break;
            case SDL_ACTIVEEVENT:
                if( event.active.state & SDL_APPACTIVE ||
                    event.active.state & SDL_APPINPUTFOCUS )
                {
                    visible = (event.active.gain == 1);
                }
            }
        }

        if(visible)
        {
            static unsigned int frame = 0;
            frame++;
            cout << "frame: " << frame << endl;
        }

        SDL_Delay( 10 );
    }

    SDL_Quit();
    return 0;
}

除了 SDL_APPACTIVE 之外，您还需要检查 SDL_APPINPUTFOCUS。