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Improve readability of V-Mapper with single-assignment.
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@hzeller
hzeller committed Mar 22, 2020
1 parent 7bcd89d commit 66fc98d
Showing 1 changed file with 13 additions and 16 deletions.
29 changes: 13 additions & 16 deletions lib/pixel-mapper.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -233,9 +233,9 @@ class VerticalMapper : public PixelMapper {
// [ O < I ] without Z [ O < I ]
// ,---^ <---- ^
// [ O < I ] [ I > O ]
// ,---^ with Z ^
// ,---^ with Z ^
// [ O < I ] ---> [ O < I ]
z_ = (param && strcmp(param, "Z") == 0) ? 1 : 0;
z_ = (param && strcasecmp(param, "Z") == 0);
return true;
}

Expand All @@ -258,20 +258,17 @@ class VerticalMapper : public PixelMapper {
int *matrix_x, int *matrix_y) const {
const int panel_width = matrix_width / chain_;
const int panel_height = matrix_height / parallel_;

*matrix_x = (x % panel_width) + int(y/panel_height)* panel_width;
*matrix_y = (y % panel_height) + int(x/panel_width) * panel_height;

const int x_panel_offset_cnt = *matrix_x / panel_width;

if (z_ && x_panel_offset_cnt % 2) {
const int x_panel_offset = x_panel_offset_cnt * panel_width;
const int y_panel_offset_cnt = *matrix_y / panel_height;
const int y_panel_offset = y_panel_offset_cnt * panel_height;

*matrix_x = panel_width - (*matrix_x - x_panel_offset) - 1 + x_panel_offset;
*matrix_y = panel_height - (*matrix_y - y_panel_offset) - 1 + y_panel_offset;
}
const int x_panel_start = y / panel_height * panel_width;
const int y_panel_start = x / panel_width * panel_height;
const int x_within_panel = x % panel_width;
const int y_within_panel = y % panel_height;
const bool needs_flipping = z_ && (y / panel_height) % 2 == 1;
*matrix_x = x_panel_start + (needs_flipping
? panel_width - 1 - x_within_panel
: x_within_panel);
*matrix_y = y_panel_start + (needs_flipping
? panel_height - 1 - y_within_panel
: y_within_panel);
}

private:
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1 comment on commit 66fc98d

@marcmerlin
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@marcmerlin marcmerlin commented on 66fc98d Mar 22, 2020 •
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Ok, now I see what you meant by your single assignment suggestion.
I think I got stuck on adding the flipping code to the existing code instead of stepping back and re-doing this from scratch as if no code were there yet.
I agree that your version is also totally readable and actually prefer your x_panel_start and x_within_panel variable names.
Thanks for the fixup.
(and yes, I verified that this works just as well)

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