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@ -25,17 +25,17 @@ typedef struct bitmap_t
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unsigned char nXDomain; /**< Last valid x-coordinate for viewport. */
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unsigned char nYDomain; /**< Last valid y-coordinate for viewport. */
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unsigned char nChunkDomain; /**< Last valid chunk for viewport. */
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unsigned char nChunkCount; /**< Amount of horiz. chunks of the bitmap. */
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unsigned char nChunkCount; /**< Amount of horiz. chunks of the bitmap.*/
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}
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bitmap_t;
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/**
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* This function generates an eight-by-one pixel chunk for a given pair of pixel
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* coordinates and a borg plane number. The resulting chunk can be copied
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* directly to the borg's frame buffer. It makes use of the user provided
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* "getChunk" function which in contrast only accepts chunk based coordinates
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* (resulting in chunks whose x-coordinates are always a multiple of eight) and
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* coordinates and a borg plane index. The resulting chunk can be copied
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* directly to the borg's frame buffer. It utilizes the user provided "getChunk"
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* function which in contrast only accepts chunk based coordinates (resulting in
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* chunks whose pixel based x-coordinates are always a multiple of eight) and
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* uses bit planes which defer from the plane scheme used by the borg's frame
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* buffer.
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* @param pBitmap The bitmap of interest.
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@ -55,25 +55,20 @@ static unsigned char bitmap_getAlignedChunk(bitmap_t const *const pBitmap,
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unsigned char nChunk = 0xFF;
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unsigned char nMask = 1;
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unsigned char const nAlignment = x % 8;
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unsigned char const x_8 = x / 8;
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// we have to go through every bit plane
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for (unsigned char i = 0; i < pBitmap->nBitPlanes; ++i)
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for (unsigned char i = pBitmap->nBitPlanes; i--;)
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{
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// generate chunk
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unsigned char nPlaneChunk;
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// if the given x-coordinate is aligned to a chunk coordinate we can
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// reuse the result of the "getChunk" function directly.
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if (nAlignment == 0)
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{
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nPlaneChunk = pBitmap->fpGetChunk(i, x/8, y, pBitmap->nFrame);
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}
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nPlaneChunk = pBitmap->fpGetChunk(i, x_8, y, pBitmap->nFrame)
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<< nAlignment;
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// in case of misalignment we combine two chunks with chunk based
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// coordinates into one chunk which aligns to the given x-coordinate
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else
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if (nAlignment != 0)
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{
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nPlaneChunk = pBitmap->fpGetChunk(i, x/8, y, pBitmap->nFrame)
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<< nAlignment;
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nPlaneChunk |= pBitmap->fpGetChunk(i, x/8+1, y, pBitmap->nFrame)
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nPlaneChunk |= pBitmap->fpGetChunk(i, x_8 + 1, y, pBitmap->nFrame)
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>> (8 - nAlignment);
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}
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@ -106,6 +101,9 @@ static void bitmap_drawViewport(bitmap_t const *const pBitmap,
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{
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for (unsigned char x = 0; x < pBitmap->nViewportWidth; x += 8)
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{
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// determine correct column within frame buffer
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unsigned char const nCol = pBitmap->nChunkCount - 1 - (x / 8);
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for (unsigned char p = NUMPLANE; p--;)
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{
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// retrieve a chunk which can be copied into the frame buffer
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@ -128,16 +126,14 @@ static void bitmap_drawViewport(bitmap_t const *const pBitmap,
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nX, nY + y) >> (8 - NUM_COLS % 8);
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}
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#endif
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// determine correct column within frame buffer
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uint8_t const nCol = pBitmap->nChunkCount - 1 - (x / 8);
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// copy chunk into corresponding frame buffer plane
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pixmap[p][y][nCol] = nChunk;
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// if a bit in plane p + 1 is set, the corresponding bit in p
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// has to be set as well
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if (p < (NUMPLANE - 1))
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{
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pixmap[p][y][nCol] |= pixmap[p + 1][y][nCol];
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nChunk |= pixmap[p + 1][y][nCol];
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}
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// copy chunk into corresponding frame buffer plane
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pixmap[p][y][nCol] = nChunk;
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}
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}
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}
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@ -215,9 +211,6 @@ void bitmap_scroll(unsigned char const nWidth,
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signed char dx = 0;
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signed char dy = 0;
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// remove garbage from screen
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clear_screen(0);
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for (bitmap.nFrame = 0; bitmap.nFrame < nFrameCount; ++bitmap.nFrame)
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{
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bitmap_drawViewport(&bitmap, x, y);
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