Atlas - SDL_windowsframebuffer.c
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2026 Sam Lantinga <[email protected]>
4
5  This software is provided 'as-is', without any express or implied
6  warranty.  In no event will the authors be held liable for any damages
7  arising from the use of this software.
8
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12
13  1. The origin of this software must not be misrepresented; you must not
14     claim that you wrote the original software. If you use this software
15     in a product, an acknowledgment in the product documentation would be
16     appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18     misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20*/
21#include "SDL_internal.h"
22
23#if defined(SDL_VIDEO_DRIVER_WINDOWS) && !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)
24
25#include "SDL_windowsvideo.h"
26
27bool WIN_CreateWindowFramebuffer(SDL_VideoDevice *_this, SDL_Window *window, SDL_PixelFormat *format, void **pixels, int *pitch)
28{
29    SDL_WindowData *data = window->internal;
30    bool isstack;
31    size_t size;
32    LPBITMAPINFO info;
33    HBITMAP hbm;
34    int w, h;
35
36    SDL_GetWindowSizeInPixels(window, &w, &h);
37
38    // Free the old framebuffer surface
39    if (data->mdc) {
40        DeleteDC(data->mdc);
41    }
42    if (data->hbm) {
43        DeleteObject(data->hbm);
44    }
45
46    // Find out the format of the screen
47    size = sizeof(BITMAPINFOHEADER) + 256 * sizeof(RGBQUAD);
48    info = (LPBITMAPINFO)SDL_small_alloc(Uint8, size, &isstack);
49    if (!info) {
50        return false;
51    }
52
53    SDL_memset(info, 0, size);
54    info->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
55
56    // The second call to GetDIBits() fills in the bitfields
57    hbm = CreateCompatibleBitmap(data->hdc, 1, 1);
58    GetDIBits(data->hdc, hbm, 0, 0, NULL, info, DIB_RGB_COLORS);
59    GetDIBits(data->hdc, hbm, 0, 0, NULL, info, DIB_RGB_COLORS);
60    DeleteObject(hbm);
61
62    // Check if a transparent channel is required
63    bool need_alpha = (window->flags & SDL_WINDOW_TRANSPARENT) != 0;
64
65    *format = SDL_PIXELFORMAT_UNKNOWN;
66    if (info->bmiHeader.biCompression == BI_BITFIELDS) {
67        int bpp;
68        Uint32 *masks;
69
70        bpp = info->bmiHeader.biPlanes * info->bmiHeader.biBitCount;
71        masks = (Uint32 *)((Uint8 *)info + info->bmiHeader.biSize);
72        *format = SDL_GetPixelFormatForMasks(bpp, masks[0], masks[1], masks[2], 0);
73    }
74    if (*format == SDL_PIXELFORMAT_UNKNOWN || need_alpha) {
75        // We'll use RGB or BGRA32 format for now
76        *format = need_alpha ? SDL_PIXELFORMAT_BGRA32 : SDL_PIXELFORMAT_XRGB8888;
77
78        // Create a new one
79        SDL_memset(info, 0, size);
80        info->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
81        info->bmiHeader.biPlanes = 1;
82        info->bmiHeader.biBitCount = 32;
83        info->bmiHeader.biCompression = need_alpha ? BI_BITFIELDS : BI_RGB;
84
85        if (need_alpha) {
86            int tmpbpp;
87            Uint32 *bgr32masks = (Uint32 *)((Uint8 *)info + info->bmiHeader.biSize);
88            SDL_GetMasksForPixelFormat(SDL_PIXELFORMAT_BGRA32, &tmpbpp, &bgr32masks[0], &bgr32masks[1], &bgr32masks[2], &bgr32masks[3]);
89        }
90    }
91
92    // Fill in the size information
93    *pitch = (((w * SDL_BYTESPERPIXEL(*format)) + 3) & ~3);
94    info->bmiHeader.biWidth = w;
95    info->bmiHeader.biHeight = -h; // negative for topdown bitmap
96    info->bmiHeader.biSizeImage = (DWORD)h * (*pitch);
97
98    data->mdc = CreateCompatibleDC(data->hdc);
99    data->hbm = CreateDIBSection(data->hdc, info, DIB_RGB_COLORS, pixels, NULL, 0);
100    SDL_small_free(info, isstack);
101
102    if (!data->hbm) {
103        return WIN_SetError("Unable to create DIB");
104    }
105    SelectObject(data->mdc, data->hbm);
106
107    return true;
108}
109
110bool WIN_UpdateWindowFramebuffer(SDL_VideoDevice *_this, SDL_Window *window, const SDL_Rect *rects, int numrects)
111{
112    SDL_WindowData *data = window->internal;
113    int i;
114
115    for (i = 0; i < numrects; ++i) {
116        BitBlt(data->hdc, rects[i].x, rects[i].y, rects[i].w, rects[i].h,
117               data->mdc, rects[i].x, rects[i].y, SRCCOPY);
118    }
119    return true;
120}
121
122void WIN_DestroyWindowFramebuffer(SDL_VideoDevice *_this, SDL_Window *window)
123{
124    SDL_WindowData *data = window->internal;
125
126    if (!data) {
127        // The window wasn't fully initialized
128        return;
129    }
130
131    if (data->mdc) {
132        DeleteDC(data->mdc);
133        data->mdc = NULL;
134    }
135    if (data->hbm) {
136        DeleteObject(data->hbm);
137        data->hbm = NULL;
138    }
139}
140
141#endif // SDL_VIDEO_DRIVER_WINDOWS
142
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