src/osx/core/glgrab.cpp

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  31  */
  32
  33 #include "wx/wxprec.h"
  34
  35 #if wxOSX_USE_COCOA_OR_CARBON
  36
  37 #import <CoreFoundation/CoreFoundation.h>
  38 #import <ApplicationServices/ApplicationServices.h>
  39 #import <OpenGL/OpenGL.h>
  40 #import <OpenGL/gl.h>
  41
  42 #include "wx/osx/core/private.h"
  43 #include "wx/osx/private/glgrab.h"
  44
  45 extern CGColorSpaceRef wxMacGetGenericRGBColorSpace();
  46
  47 /*
  48  * perform an in-place swap from Quadrant 1 to Quadrant III format
  49  * (upside-down PostScript/GL to right side up QD/CG raster format)
  50  * We do this in-place, which requires more copying, but will touch
  51  * only half the pages.  (Display grabs are BIG!)
  52  *
  53  * Pixel reformatting may optionally be done here if needed.
  54  */
  55 static void swizzleBitmap(void * data, int rowBytes, int height)
  56 {
  57     int top, bottom;
  58     void * buffer;
  59     void * topP;
  60     void * bottomP;
  61     void * base;
  62
  63
  64     top = 0;
  65     bottom = height - 1;
  66     base = data;
  67     buffer = malloc(rowBytes);
  68
  69
  70     while ( top < bottom )
  71     {
  72         topP = (void *)((top * rowBytes) + (intptr_t)base);
  73         bottomP = (void *)((bottom * rowBytes) + (intptr_t)base);
  74
  75
  76         /*
  77          * Save and swap scanlines.
  78          *
  79          * This code does a simple in-place exchange with a temp buffer.
  80          * If you need to reformat the pixels, replace the first two bcopy()
  81          * calls with your own custom pixel reformatter.
  82          */
  83         bcopy( topP, buffer, rowBytes );
  84         bcopy( bottomP, topP, rowBytes );
  85         bcopy( buffer, bottomP, rowBytes );
  86
  87         ++top;
  88         --bottom;
  89     }
  90     free( buffer );
  91 }
  92
  93
  94 /*
  95  * Given a display ID and a rectangle on that display, generate a CGImageRef
  96  * containing the display contents.
  97  *
  98  * srcRect is display-origin relative.
  99  *
 100  * This function uses a full screen OpenGL read-only context.
 101  * By using OpenGL, we can read the screen using a DMA transfer
 102  * when it's in millions of colors mode, and we can correctly read
 103  * a microtiled full screen OpenGL context, such as a game or full
 104  * screen video display.
 105  *
 106  * Returns a CGImageRef. When you are done with the CGImageRef, release it
 107  * using CFRelease().
 108  * Returns NULL on an error.
 109  */
 110
 111 CGImageRef grabViaOpenGL(CGDirectDisplayID display, CGRect srcRect)
 112 {
 113     CGContextRef bitmap;
 114     CGImageRef image;
 115     void * data;
 116     long bytewidth;
 117     GLint width, height;
 118     long bytes;
 119
 120     CGLContextObj    glContextObj;
 121     CGLPixelFormatObj pixelFormatObj ;
 122     GLint numPixelFormats ;
 123     CGLPixelFormatAttribute attribs[] =
 124     {
 125         kCGLPFAFullScreen,
 126         kCGLPFADisplayMask,
 127         (CGLPixelFormatAttribute) 0,    /* Display mask bit goes here */
 128         (CGLPixelFormatAttribute) 0
 129     } ;
 130
 131
 132     if ( display == kCGNullDirectDisplay )
 133         display = CGMainDisplayID();
 134     attribs[2] = (CGLPixelFormatAttribute) CGDisplayIDToOpenGLDisplayMask(display);
 135
 136
 137     /* Build a full-screen GL context */
 138     CGLChoosePixelFormat( attribs, &pixelFormatObj, &numPixelFormats );
 139     if ( pixelFormatObj == NULL )    // No full screen context support
 140         return NULL;
 141     CGLCreateContext( pixelFormatObj, NULL, &glContextObj ) ;
 142     CGLDestroyPixelFormat( pixelFormatObj ) ;
 143     if ( glContextObj == NULL )
 144         return NULL;
 145
 146
 147     CGLSetCurrentContext( glContextObj ) ;
 148     CGLSetFullScreen( glContextObj ) ;
 149
 150
 151     glReadBuffer(GL_FRONT);
 152
 153
 154     width = (GLint)srcRect.size.width;
 155     height = (GLint)srcRect.size.height;
 156
 157
 158     bytewidth = width * 4; // Assume 4 bytes/pixel for now
 159     bytewidth = (bytewidth + 3) & ~3; // Align to 4 bytes
 160     bytes = bytewidth * height; // width * height
 161
 162     /* Build bitmap context */
 163     data = malloc(height * bytewidth);
 164     if ( data == NULL )
 165     {
 166         CGLSetCurrentContext( NULL );
 167         CGLClearDrawable( glContextObj ); // disassociate from full screen
 168         CGLDestroyContext( glContextObj ); // and destroy the context
 169         return NULL;
 170     }
 171     bitmap = CGBitmapContextCreate(data, width, height, 8, bytewidth,
 172                                    wxMacGetGenericRGBColorSpace(), kCGImageAlphaNoneSkipFirst /* XRGB */);
 173
 174
 175     /* Read framebuffer into our bitmap */
 176     glFinish(); /* Finish all OpenGL commands */
 177     glPixelStorei(GL_PACK_ALIGNMENT, 4); /* Force 4-byte alignment */
 178     glPixelStorei(GL_PACK_ROW_LENGTH, 0);
 179     glPixelStorei(GL_PACK_SKIP_ROWS, 0);
 180     glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
 181
 182     /*
 183      * Fetch the data in XRGB format, matching the bitmap context.
 184      */
 185     glReadPixels((GLint)srcRect.origin.x, (GLint)srcRect.origin.y, width, height,
 186                  GL_BGRA,
 187 #ifdef __BIG_ENDIAN__
 188                  GL_UNSIGNED_INT_8_8_8_8_REV, // for PPC
 189 #else
 190                  GL_UNSIGNED_INT_8_8_8_8, // for Intel! http://lists.apple.com/archives/quartz-dev/2006/May/msg00100.html
 191 #endif
 192                  data);
 193     /*
 194      * glReadPixels generates a quadrant I raster, with origin in the lower left
 195      * This isn't a problem for signal processing routines such as compressors,
 196      * as they can simply use a negative 'advance' to move between scanlines.
 197      * CGImageRef and CGBitmapContext assume a quadrant III raster, though, so we need to
 198      * invert it. Pixel reformatting can also be done here.
 199      */
 200     swizzleBitmap(data, bytewidth, height);
 201
 202
 203     /* Make an image out of our bitmap; does a cheap vm_copy of the bitmap */
 204     image = CGBitmapContextCreateImage(bitmap);
 205
 206     /* Get rid of bitmap */
 207     CFRelease(bitmap);
 208     free(data);
 209
 210
 211     /* Get rid of GL context */
 212     CGLSetCurrentContext( NULL );
 213     CGLClearDrawable( glContextObj ); // disassociate from full screen
 214     CGLDestroyContext( glContextObj ); // and destroy the context
 215
 216     /* Returned image has a reference count of 1 */
 217     return image;
 218 }
 219
 220 #endif