rockorager.dev
an experimental irc client
ui: fix scrollbar integer overflow on channels with lots of messages
Reported-by: erk on IRC
+5
-2
src/Scrollbar.zig
+5
-2
src/Scrollbar.zig
···
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@memset(surface.buffer, empty);
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// (view_size / total) * window height = size of the scroll bar
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-
const bar_height = @max(std.math.divCeil(usize, self.view_size * max.height, self.total) catch unreachable, 1);
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+
const premul1 = std.math.mulWide(u16, self.view_size, max.height);
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+
const bar_height = @max(std.math.divCeil(usize, premul1, self.total) catch unreachable, 1);
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+
// Premultiply. We use mulWide to ensure we never overflow
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+
const premul2 = std.math.mulWide(u16, self.bottom, max.height);
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// The row of the last cell of the bottom of the bar
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const bar_bottom = (max.height - 1) -| (std.math.divCeil(usize, self.bottom * max.height, self.total) catch unreachable);
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+
const bar_bottom = (max.height - 1) -| (std.math.divCeil(usize, premul2, self.total) catch unreachable);
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var i: usize = 0;
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while (i <= bar_height) : (i += 1)