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image: Fix high-res mouse wheel zoom

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High res scrolling is reported as wheel deltas < 1. Use a
formula that works for all delta values.

Closes #63
This commit is contained in:
Sophie Herold 2023-03-01 02:17:10 +01:00
parent 5bcf534142
commit 257d154f08
1 changed files with 14 additions and 12 deletions
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26
src/widgets/image.rs
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@ -37,10 +37,12 @@ const ROTATION_ANIMATION_DURATION: u32 = 200;
/// Relative to current zoom level
const ZOOM_FACTOR_BUTTON: f64 = 1.5;
/// Relative to current zoom level
const ZOOM_FACTOR_WHEEL: f64 = 1.3;
/// Relative to current zoom level
const ZOOM_FACTOR_WHEEL_HI_RES: f64 = 0.001;
/// Zoom 30% per scroll wheel detent
const ZOOM_FACTOR_SCROLL_WHEEL: f64 = 1.3;
/// Zoom 0.5% per pixel
///
/// This is for scrolling devices that might not exist
const ZOOM_FACTOR_SCROLL_SURFACE: f64 = 1.005;
/// Relative to best-fit level
const ZOOM_FACTOR_DOUBLE_TAP: f64 = 2.5;
@ -276,21 +278,19 @@ mod imp {
return gtk::Inhibit(false);
}
// Use exponential scaling since zoom is always multiplicative with the existing value
// This is the right thing since `exp(n/2)^2 == exp(n)` (two small steps are the same as one larger step)
let (zoom_factor, animated) = match event.unit() {
gdk::ScrollUnit::Wheel => (y.abs() * ZOOM_FACTOR_WHEEL, true),
// TODO: completely untested
gdk::ScrollUnit::Surface => (y.abs() * ZOOM_FACTOR_WHEEL_HI_RES + 1.0, false),
gdk::ScrollUnit::Wheel => (f64::exp( - y * f64::ln(ZOOM_FACTOR_SCROLL_WHEEL)), y.abs() >= 1.),
gdk::ScrollUnit::Surface => (f64::exp( - y * f64::ln(ZOOM_FACTOR_SCROLL_SURFACE)), false),
unknown_unit => {
log::warn!("Ignoring unknown scroll unit: {unknown_unit}");
(1., false)
}
};
let zoom = if y > 0. {
obj.imp().zoom_target.get() / zoom_factor
} else {
obj.imp().zoom_target.get() * zoom_factor
};
let zoom =
obj.imp().zoom_target.get() * zoom_factor;
if zoom > obj.zoom_level_best_fit() {
obj.set_best_fit(false);
@ -298,6 +298,7 @@ mod imp {
obj.zoom_to(zoom);
} else {
obj.set_zoom(zoom);
obj.imp().zoom_target.set(zoom);
}
} else {
obj.set_best_fit(true);
@ -305,6 +306,7 @@ mod imp {
obj.zoom_to(obj.zoom_level_best_fit());
} else {
obj.set_zoom(obj.zoom_level_best_fit());
obj.imp().zoom_target.set(obj.zoom_level_best_fit());
}
}