通过拖动边框调整大小时不会出现SDL_WINDOWEVENT_SIZE_CHANGED？答案

【问题标题】：SDL_WINDOWEVENT_SIZE_CHANGED does not appear when resize by dragging border?通过拖动边框调整大小时不会出现SDL_WINDOWEVENT_SIZE_CHANGED？
【发布时间】：2019-10-08 01:47:49
【问题描述】：

我在 Windows 上使用 SDL2。我正在尝试获得这样的调整大小事件。

#include "SDL/SDL.h"
#include <iostream>
int main(int argc, char** argv) {
    SDL_Window* window = SDL_CreateWindow("title", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,800, 500, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
    while (true) {
        SDL_Event sdl_event;
        if (SDL_WaitEvent(&sdl_event)) {
            if (sdl_event.key.repeat == 0) { // no repeat event
                switch (sdl_event.type) {
                case SDL_QUIT:
                {
                    break;
                }
                case SDL_WINDOWEVENT:
                {
                    if (sdl_event.window.event == SDL_WINDOWEVENT_SIZE_CHANGED){
                        std::cout << sdl_event.window.data1 << " " << sdl_event.window.data2 << "\n";
                    }
                    break;
                }
                }
            }
        }
    }
    return 0;
}

但是当我尝试通过拖动边框来调整窗口大小时，我没有收到该事件。但是，当我使用最大化按钮时，我确实收到了该事件。怎么了？

【问题讨论】：

操作系统？ SDL 版本？ minimal reproducible example?
@genpfault 我已经编辑了问题以包含必要的信息
@HarryKane 您没有添加 SDL 版本。我假设是 2.0.10？

标签： c++ sdl

【解决方案1】：

ZhuYaDong's SDL_AddEventWatch() approach 在这个 Windows 10 机器上工作：

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

int resizingEventWatcher( void* data, SDL_Event* event )
{
    SDL_Window* window = static_cast< SDL_Window* >( data );
    SDL_Event& ev = *event;

    if( ev.type == SDL_WINDOWEVENT &&
        ev.window.event == SDL_WINDOWEVENT_RESIZED )
    {
        if( SDL_GetWindowFromID( ev.window.windowID ) == window )
        {
            std::cout << std::this_thread::get_id() << ": " << ev.window.data1 << " " << ev.window.data2 << std::endl;
        }
    }
    return 0;
}

int main( int argc, char** argv )
{
    SDL_Init( SDL_INIT_EVERYTHING );

    SDL_Window* window = SDL_CreateWindow
        (
        "title",
        SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
        800, 500,
        SDL_WINDOW_RESIZABLE
        );
    SDL_AddEventWatch( resizingEventWatcher, window );

    bool running = true;
    while( running )
    {
        SDL_Event ev;
        while( SDL_PollEvent( &ev ) )
        {
            switch( ev.type )
            {
            case SDL_QUIT:
                running = false;
                break;
            case SDL_WINDOWEVENT:
                if( ev.window.event == SDL_WINDOWEVENT_SIZE_CHANGED )
                {
                    std::cout << std::this_thread::get_id() << ": "<< ev.window.data1 << " " << ev.window.data2 << std::endl;
                }
                break;
            }
        }
    }
    return 0;
}

~~如果你想变得花哨，你可以在resizingEventWatcher() 中创建一个用户事件，并使用SDL_PushEvent() 将其发布到主事件队列。~~ 编辑： 遗憾的是这些用户事件似乎只是在调整大小期间排队，并且在您停止调整窗口大小之前不会进入主事件处理循环：

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

Uint32 ResizingEvent = 0;
int resizingEventWatcher( void* data, SDL_Event* event )
{
    SDL_Event& ev = *event;
    if( ev.type == SDL_WINDOWEVENT &&
        ev.window.event == SDL_WINDOWEVENT_RESIZED )
    {
        SDL_Event newEvent = { 0 };
        newEvent.type = ResizingEvent;
        newEvent.user.windowID = ev.window.windowID;
        newEvent.user.data1 = reinterpret_cast< void* >( ev.window.data1 );
        newEvent.user.data2 = reinterpret_cast< void* >( ev.window.data2 );
        SDL_PushEvent( &newEvent );
    }
    return 0;
}

int main( int argc, char** argv )
{
    SDL_Init( SDL_INIT_EVERYTHING );
    ResizingEvent = SDL_RegisterEvents( 1 );

    SDL_Window* window = SDL_CreateWindow
        (
        "title",
        SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
        800, 500,
        SDL_WINDOW_RESIZABLE
        );
    SDL_AddEventWatch( resizingEventWatcher, window );

    bool running = true;
    while( running )
    {
        SDL_Event ev;
        while( SDL_PollEvent( &ev ) )
        {
            switch( ev.type )
            {
            case SDL_QUIT:
                running = false;
                break;
            case SDL_WINDOWEVENT:
                if( ev.window.event == SDL_WINDOWEVENT_SIZE_CHANGED )
                {
                    std::cout << std::this_thread::get_id() << ": "<< ev.window.data1 << " " << ev.window.data2 << std::endl;
                }
                break;
            case SDL_USEREVENT:
                if( ev.user.type == ResizingEvent )
                {
                    std::cout << std::this_thread::get_id() << ": "<< reinterpret_cast< Sint32 >( ev.user.data1 ) << " " << reinterpret_cast< Sint32 >( ev.user.data2 ) << std::endl;
                }
                break;
            }
        }
    }
    return 0;
}

（使用 SDL 的 release-2.0.10 tag）

【讨论】：