/* Function Definitions */
void b_log2(const double x[2], double f[2])
{
int k;
for (k = 0; k < 2; k++) {
f[k] = scalar_log2(x[k]);
}
}
// The goal of the powers of two tiles is to minimize the amount of wasted tile
// space in the width-wise direction and then minimize the number of tiles. The
// constraints are that every tile must have a pixel width that is a power of
// two and also be of some minimal width (that is also a power of two).
//
// This is solved by first taking our picture size and rounding it up to the
// multiple of the minimal width. The binary representation of this rounded
// value gives us the tiles we need: a bit of value one means we need a tile of
// that size.
void TiledPictureRenderer::setupPowerOf2Tiles() {
// Only use enough tiles to cover the viewport
const int width = this->getViewWidth();
const int height = this->getViewHeight();
int rounded_value = width;
if (width % fTileMinPowerOf2Width != 0) {
rounded_value = width - (width % fTileMinPowerOf2Width) + fTileMinPowerOf2Width;
}
int num_bits = SkScalarCeilToInt(scalar_log2(SkIntToScalar(width)));
int largest_possible_tile_size = 1 << num_bits;
fTilesX = fTilesY = 0;
// The tile height is constant for a particular picture.
for (int tile_y_start = 0; tile_y_start < height; tile_y_start += fTileHeight) {
fTilesY++;
int tile_x_start = 0;
int current_width = largest_possible_tile_size;
// Set fTileWidth to be the width of the widest tile, so that each canvas is large enough
// to draw each tile.
fTileWidth = current_width;
while (current_width >= fTileMinPowerOf2Width) {
// It is very important this is a bitwise AND.
if (current_width & rounded_value) {
if (0 == tile_y_start) {
// Only count tiles in the X direction on the first pass.
fTilesX++;
}
*fTileRects.append() = SkRect::MakeXYWH(SkIntToScalar(tile_x_start),
SkIntToScalar(tile_y_start),
SkIntToScalar(current_width),
SkIntToScalar(fTileHeight));
tile_x_start += current_width;
}
current_width >>= 1;
}
}
}
