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Codechange: refactor CalcHeightdiff to remove some magic numbers

This commit is contained in:
Rubidium 2024-04-27 21:25:15 +02:00
parent 440a633fcc
commit 7558bd7e87
1 changed files with 37 additions and 28 deletions
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65
src/viewport.cpp
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@ -2887,19 +2887,18 @@ static int CalcHeightdiff(HighLightStyle style, uint distance, TileIndex start_t
if (swap) Swap(start_tile, end_tile);
switch (style & HT_DRAG_MASK) {
case HT_RECT: {
static const TileIndexDiffC heightdiff_area_by_dir[] = {
/* Start */ {1, 0}, /* Dragging east */ {0, 0}, // Dragging south
/* End */ {0, 1}, /* Dragging east */ {1, 1} // Dragging south
};
case HT_RECT:
/* In the case of an area we can determine whether we were dragging south or
* east by checking the X-coordinates of the tiles */
uint8_t style_t = (uint8_t)(TileX(end_tile) > TileX(start_tile));
start_tile = TileAdd(start_tile, ToTileIndexDiff(heightdiff_area_by_dir[style_t]));
end_tile = TileAdd(end_tile, ToTileIndexDiff(heightdiff_area_by_dir[2 + style_t]));
if (TileX(end_tile) > TileX(start_tile)) {
/* Dragging south does not need to change the start tile. */
end_tile = TileAddByDir(end_tile, DIR_S);
} else {
/* Dragging east. */
start_tile = TileAddByDir(start_tile, DIR_SW);
end_tile = TileAddByDir(end_tile, DIR_SE);
}
[[fallthrough]];
}
case HT_POINT:
h0 = TileHeight(start_tile);
@ -2909,18 +2908,28 @@ static int CalcHeightdiff(HighLightStyle style, uint distance, TileIndex start_t
static const HighLightStyle flip_style_direction[] = {
HT_DIR_X, HT_DIR_Y, HT_DIR_HL, HT_DIR_HU, HT_DIR_VR, HT_DIR_VL
};
static const TileIndexDiffC heightdiff_line_by_dir[] = {
/* Start */ {1, 0}, {1, 1}, /* HT_DIR_X */ {0, 1}, {1, 1}, // HT_DIR_Y
/* Start */ {1, 0}, {0, 0}, /* HT_DIR_HU */ {1, 0}, {1, 1}, // HT_DIR_HL
/* Start */ {1, 0}, {1, 1}, /* HT_DIR_VL */ {0, 1}, {1, 1}, // HT_DIR_VR
/* Start */ {0, 1}, {0, 0}, /* HT_DIR_X */ {1, 0}, {0, 0}, // HT_DIR_Y
/* End */ {0, 1}, {0, 0}, /* HT_DIR_HU */ {1, 1}, {0, 1}, // HT_DIR_HL
/* End */ {1, 0}, {0, 0}, /* HT_DIR_VL */ {0, 0}, {0, 1}, // HT_DIR_VR
static const std::pair<TileIndexDiffC, TileIndexDiffC> start_heightdiff_line_by_dir[] = {
{ {1, 0}, {1, 1} }, // HT_DIR_X
{ {0, 1}, {1, 1} }, // HT_DIR_Y
{ {1, 0}, {0, 0} }, // HT_DIR_HU
{ {1, 0}, {1, 1} }, // HT_DIR_HL
{ {1, 0}, {1, 1} }, // HT_DIR_VL
{ {0, 1}, {1, 1} }, // HT_DIR_VR
};
static const std::pair<TileIndexDiffC, TileIndexDiffC> end_heightdiff_line_by_dir[] = {
{ {0, 1}, {0, 0} }, // HT_DIR_X
{ {1, 0}, {0, 0} }, // HT_DIR_Y
{ {0, 1}, {0, 0} }, // HT_DIR_HU
{ {1, 1}, {0, 1} }, // HT_DIR_HL
{ {1, 0}, {0, 0} }, // HT_DIR_VL
{ {0, 0}, {0, 1} }, // HT_DIR_VR
};
static_assert(std::size(start_heightdiff_line_by_dir) == HT_DIR_END);
static_assert(std::size(end_heightdiff_line_by_dir) == HT_DIR_END);
distance %= 2; // we're only interested if the distance is even or uneven
style &= HT_DIR_MASK;
assert(style < HT_DIR_END);
/* To handle autorail, we do some magic to be able to use a lookup table.
* Firstly if we drag the other way around, we switch start&end, and if needed
@ -2928,20 +2937,20 @@ static int CalcHeightdiff(HighLightStyle style, uint distance, TileIndex start_t
* that means the end, which is now the start is on the right */
if (swap && distance == 0) style = flip_style_direction[style];
/* Lambda to help calculating the height at one side of the line. */
auto get_height = [](auto &tile, auto &heightdiffs) {
return std::max(
TileHeight(TileAdd(tile, ToTileIndexDiff(heightdiffs.first))),
TileHeight(TileAdd(tile, ToTileIndexDiff(heightdiffs.second))));
};
/* Use lookup table for start-tile based on HighLightStyle direction */
uint8_t style_t = style * 2;
assert(style_t < lengthof(heightdiff_line_by_dir) - 13);
h0 = TileHeight(TileAdd(start_tile, ToTileIndexDiff(heightdiff_line_by_dir[style_t])));
uint ht = TileHeight(TileAdd(start_tile, ToTileIndexDiff(heightdiff_line_by_dir[style_t + 1])));
h0 = std::max(h0, ht);
h0 = get_height(start_tile, start_heightdiff_line_by_dir[style]);
/* Use lookup table for end-tile based on HighLightStyle direction
* flip around side (lower/upper, left/right) based on distance */
if (distance == 0) style_t = flip_style_direction[style] * 2;
assert(style_t < lengthof(heightdiff_line_by_dir) - 13);
h1 = TileHeight(TileAdd(end_tile, ToTileIndexDiff(heightdiff_line_by_dir[12 + style_t])));
ht = TileHeight(TileAdd(end_tile, ToTileIndexDiff(heightdiff_line_by_dir[12 + style_t + 1])));
h1 = std::max(h1, ht);
if (distance == 0) style = flip_style_direction[style];
h1 = get_height(end_tile, end_heightdiff_line_by_dir[style]);
break;
}
}