Do less rounding of positions to pixel boundaries

Fixes https://github.com/emilk/egui/issues/27

CHANGELOG.md

@@ -6,6 +6,7 @@
 * Add ability to override text color with `visuals.override_text_color`
 * Refactored the interface for `egui::app::App`
 * Demo App: Add slider to scale all of Egui
+* Fix a bug where some regions would slowly grow for non-integral scales (`pixels_per_point`).
 
 ## 0.2.0 - 2020-10-10
 

egui/src/containers/area.rs

@@ -173,7 +173,7 @@ impl Prepared {
             movable,
         } = self;
 
-        state.size = (content_ui.min_rect().max - state.pos).ceil();
+        state.size = content_ui.min_rect().size();
 
         let rect = Rect::from_min_size(state.pos, state.size);
         let clip_rect = Rect::everything(); // TODO: get from context

egui/src/containers/resize.rs

@@ -240,7 +240,6 @@ impl Resize {
         } = prepared;
 
         state.last_content_size = content_ui.min_size();
-        state.last_content_size = state.last_content_size.ceil(); // Avoid rounding errors in math
 
         // ------------------------------
 
@@ -249,7 +248,6 @@ impl Resize {
             // so we must follow the contents:
 
             state.desired_size = state.desired_size.max(state.last_content_size);
-            state.desired_size = ui.painter().round_vec_to_pixels(state.desired_size);
 
             // We are as large as we look
             ui.allocate_space(state.desired_size);

egui/src/ui.rs

@@ -438,9 +438,6 @@ impl Ui {
     ///
     /// You may get LESS space than you asked for if the current layout won't fit what you asked for.
     pub fn allocate_space(&mut self, desired_size: Vec2) -> Rect {
-        let desired_size = self.painter().round_vec_to_pixels(desired_size);
-        self.cursor = self.painter().round_pos_to_pixels(self.cursor);
-
         // For debug rendering
         let too_wide = desired_size.x > self.available().width();
         let too_high = desired_size.x > self.available().height();