video-pc/libs/Recorder/record_desktop_mag.h

#pragma once

// documents
// https://learn.microsoft.com/en-us/previous-versions/windows/desktop/magapi/magapi-intro
// https://learn.microsoft.com/en-us/previous-versions/windows/desktop/magapi/magapi-whats-new
// https://github.com/microsoft/Windows-classic-samples/blob/main/Samples/Magnification/cpp/Windowed/MagnifierSample.cpp

#include <magnification.h>

#include "record_desktop.h"

namespace am {
class record_desktop_mag : public record_desktop
{
    typedef BOOL(WINAPI *MagImageScalingCallback)(HWND hwnd,
                                                  void *srcdata,
                                                  MAGIMAGEHEADER srcheader,
                                                  void *destdata,
                                                  MAGIMAGEHEADER destheader,
                                                  RECT unclipped,
                                                  RECT clipped,
                                                  HRGN dirty);
    typedef BOOL(WINAPI *MagInitializeFunc)(void);
    typedef BOOL(WINAPI *MagUninitializeFunc)(void);
    typedef BOOL(WINAPI *MagSetWindowSourceFunc)(HWND hwnd, RECT rect);
    typedef BOOL(WINAPI *MagSetWindowFilterListFunc)(HWND hwnd,
                                                     DWORD dwFilterMode,
                                                     int count,
                                                     HWND *pHWND);
    typedef BOOL(WINAPI *MagSetImageScalingCallbackFunc)(HWND hwnd,
                                                         MagImageScalingCallback callback);

    static BOOL WINAPI on_mag_scaling_callback(HWND hwnd,
                                               void *srcdata,
                                               MAGIMAGEHEADER srcheader,
                                               void *destdata,
                                               MAGIMAGEHEADER destheader,
                                               RECT unclipped,
                                               RECT clipped,
                                               HRGN dirty);

public:
    record_desktop_mag();
    ~record_desktop_mag() override;

    int init(const RECORD_DESKTOP_RECT &rect, const int fps) override;

    int start() override;
    int pause() override;
    int resume() override;
    int stop() override;

    void set_exclude(HWND excluded_window);

protected:
    void clean_up() override;

private:
    void record_func();

    void do_sleep(int64_t dur, int64_t pre, int64_t now);

    bool do_mag_initialize();

    int do_mag_record();

    void on_mag_data(void *data, const MAGIMAGEHEADER &header);

    bool seh_mag_set_window_source(HWND hwnd, RECT rect, DWORD &exception);

private:
    uint32_t _width = 0;
    uint32_t _height = 0;
    int64_t _current_pts = -1;

    // Used to exclude window with specified window id.
    HWND _excluded_window = NULL;

    // Used for getting the screen dpi.
    HDC _desktop_dc = NULL;

    // Module handler
    HMODULE _mag_lib_handle = NULL;

    // Mag functions
    MagInitializeFunc _mag_initialize_func = nullptr;
    MagUninitializeFunc _mag_uninitialize_func = nullptr;
    MagSetWindowSourceFunc _mag_set_window_source_func = nullptr;
    MagSetWindowFilterListFunc _mag_set_window_filter_list_func = nullptr;
    MagSetImageScalingCallbackFunc _mag_set_image_scaling_callback_func = nullptr;

    // The hidden window hosting the magnifier control.
    HWND _host_window = NULL;

    // The magnifier control that captures the screen.
    HWND _magnifier_window = NULL;

    // True if the magnifier control has been successfully initialized.
    bool _magnifier_initialized = false;

    // True if the last OnMagImageScalingCallback was called and handled
    // successfully. Reset at the beginning of each CaptureImage call.
    bool _magnifier_capture_succeeded = true;
};
} // namespace am