[egui] Clean up Painter interface

egui/src/containers/collapsing_header.rs

@@ -235,7 +235,7 @@ impl CollapsingHeader {
         }
 
         let painter = ui.painter();
-        painter.add_galley(
+        painter.galley(
             text_pos,
             galley,
             label.text_style,

egui/src/context.rs

@@ -125,14 +125,17 @@ impl Context {
         (point * self.input.pixels_per_point).round() / self.input.pixels_per_point
     }
 
+    /// Useful for pixel-perfect rendering
     pub fn round_pos_to_pixels(&self, pos: Pos2) -> Pos2 {
         pos2(self.round_to_pixel(pos.x), self.round_to_pixel(pos.y))
     }
 
+    /// Useful for pixel-perfect rendering
     pub fn round_vec_to_pixels(&self, vec: Vec2) -> Vec2 {
         vec2(self.round_to_pixel(vec.x), self.round_to_pixel(vec.y))
     }
 
+    /// Useful for pixel-perfect rendering
     pub fn round_rect_to_pixels(&self, rect: Rect) -> Rect {
         Rect {
             min: self.round_pos_to_pixels(rect.min),

egui/src/layout.rs

@@ -39,13 +39,13 @@ impl Default for Align {
 
 /// Used e.g. to anchor a piece of text to a part of the rectangle.
 /// Give a position within the rect, specified by the aligns
-pub(crate) fn align_rect(rect: Rect, align: (Align, Align)) -> Rect {
+pub(crate) fn anchor_rect(rect: Rect, anchor: (Align, Align)) -> Rect {
-    let x = match align.0 {
+    let x = match anchor.0 {
         Align::Min => rect.left(),
         Align::Center => rect.left() - 0.5 * rect.width(),
         Align::Max => rect.left() - rect.width(),
     };
-    let y = match align.1 {
+    let y = match anchor.1 {
         Align::Min => rect.top(),
         Align::Center => rect.top() - 0.5 * rect.height(),
         Align::Max => rect.top() - rect.height(),

egui/src/math.rs

@@ -21,6 +21,12 @@ impl From<[f32; 2]> for Vec2 {
     }
 }
 
+impl From<&[f32; 2]> for Vec2 {
+    fn from(v: &[f32; 2]) -> Self {
+        Self { x: v[0], y: v[1] }
+    }
+}
+
 impl Vec2 {
     pub fn zero() -> Self {
         Self { x: 0.0, y: 0.0 }
@@ -245,7 +251,17 @@ impl From<[f32; 2]> for Pos2 {
     }
 }
 
+impl From<&[f32; 2]> for Pos2 {
+    fn from(v: &[f32; 2]) -> Self {
+        Self { x: v[0], y: v[1] }
+    }
+}
+
 impl Pos2 {
+    pub fn new(x: f32, y: f32) -> Self {
+        Self { x, y }
+    }
+
     pub fn to_vec2(self) -> Vec2 {
         Vec2 {
             x: self.x,
@@ -492,6 +508,9 @@ impl Rect {
     pub fn height(&self) -> f32 {
         self.max.y - self.min.y
     }
+    pub fn area(&self) -> f32 {
+        self.width() * self.height()
+    }
 
     pub fn range_x(&self) -> RangeInclusive<f32> {
         self.min.x..=self.max.x

egui/src/paint/command.rs

@@ -10,9 +10,9 @@ pub enum PaintCmd {
     Noop,
     Circle {
         center: Pos2,
+        radius: f32,
         fill: Option<Color>,
         outline: Option<LineStyle>,
-        radius: f32,
     },
     LineSegment {
         points: [Pos2; 2],
@@ -48,6 +48,24 @@ impl PaintCmd {
             style: LineStyle::new(width, color),
         }
     }
+
+    pub fn circle_filled(center: Pos2, radius: f32, fill_color: Color) -> Self {
+        Self::Circle {
+            center,
+            radius,
+            fill: Some(fill_color),
+            outline: None,
+        }
+    }
+
+    pub fn circle_outline(center: Pos2, radius: f32, outline: LineStyle) -> Self {
+        Self::Circle {
+            center,
+            radius,
+            fill: None,
+            outline: Some(outline),
+        }
+    }
 }
 
 #[derive(Clone, Copy, Debug)]

egui/src/painter.rs

@@ -1,7 +1,7 @@
 use std::sync::Arc;
 
 use crate::{
-    align_rect, color,
+    anchor_rect, color,
     layers::PaintCmdIdx,
     math::{Pos2, Rect, Vec2},
     paint::{font, Fonts, LineStyle, PaintCmd, TextStyle},
@@ -30,16 +30,24 @@ impl Painter {
             clip_rect,
         }
     }
+
+    /// Create a painter for a sub-region of this `Painter`.
+    ///
+    /// The clip-rect of the returned `Painter` will be the intersection
+    /// of the given rectangle and the `clip_rect()` of this `Painter`.
+    pub fn sub_region(&self, rect: Rect) -> Self {
+        Self::new(self.ctx.clone(), self.layer, rect.intersect(self.clip_rect))
+    }
 }
 
 /// ## Accessors etc
 impl Painter {
-    pub fn ctx(&self) -> &Arc<Context> {
+    pub(crate) fn ctx(&self) -> &Arc<Context> {
         &self.ctx
     }
 
     /// Available fonts
-    pub fn fonts(&self) -> &Fonts {
+    pub(crate) fn fonts(&self) -> &Fonts {
         self.ctx.fonts()
     }
 
@@ -60,14 +68,17 @@ impl Painter {
         self.clip_rect = clip_rect;
     }
 
+    /// Useful for pixel-perfect rendering
     pub fn round_to_pixel(&self, point: f32) -> f32 {
         self.ctx().round_to_pixel(point)
     }
 
+    /// Useful for pixel-perfect rendering
     pub fn round_vec_to_pixels(&self, vec: Vec2) -> Vec2 {
         self.ctx().round_vec_to_pixels(vec)
     }
 
+    /// Useful for pixel-perfect rendering
     pub fn round_pos_to_pixels(&self, pos: Pos2) -> Pos2 {
         self.ctx().round_pos_to_pixels(pos)
     }
@@ -110,51 +121,52 @@ impl Painter {
             outline: Some(LineStyle::new(1.0, color)),
             rect,
         });
-        let align = (Align::Min, Align::Min);
+        let anchor = (Align::Min, Align::Min);
         let text_style = TextStyle::Monospace;
-        self.floating_text(rect.min, text.into(), text_style, align, color);
+        self.text(rect.min, anchor, text.into(), text_style, color);
     }
 
     pub fn error(&self, pos: Pos2, text: impl Into<String>) {
         let text = text.into();
-        let align = (Align::Min, Align::Min);
+        let anchor = (Align::Min, Align::Min);
         let text_style = TextStyle::Monospace;
         let font = &self.fonts()[text_style];
         let galley = font.layout_multiline(text, f32::INFINITY);
-        let rect = align_rect(Rect::from_min_size(pos, galley.size), align);
+        let rect = anchor_rect(Rect::from_min_size(pos, galley.size), anchor);
         self.add(PaintCmd::Rect {
             corner_radius: 0.0,
             fill: Some(color::gray(0, 240)),
             outline: Some(LineStyle::new(1.0, color::RED)),
             rect: rect.expand(2.0),
         });
-        self.add_galley(rect.min, galley, text_style, color::RED);
+        self.galley(rect.min, galley, text_style, color::RED);
     }
 }
 
 /// ## Text
 impl Painter {
-    /// Show some text anywhere in the ui.
+    /// Lay out and paint some text.
-    /// To center the text at the given position, use `align: (Center, Center)`.
+    ///
-    /// If you want to draw text floating on top of everything,
+    /// To center the text at the given position, use `anchor: (Center, Center)`.
-    /// consider using `Context.floating_text` instead.
+    ///
-    pub fn floating_text(
+    /// Returns where the text ended up.
+    pub fn text(
         &self,
         pos: Pos2,
+        anchor: (Align, Align),
         text: impl Into<String>,
         text_style: TextStyle,
-        align: (Align, Align),
         text_color: Color,
     ) -> Rect {
         let font = &self.fonts()[text_style];
         let galley = font.layout_multiline(text.into(), f32::INFINITY);
-        let rect = align_rect(Rect::from_min_size(pos, galley.size), align);
+        let rect = anchor_rect(Rect::from_min_size(pos, galley.size), anchor);
-        self.add_galley(rect.min, galley, text_style, text_color);
+        self.galley(rect.min, galley, text_style, text_color);
         rect
     }
 
-    /// Already layed out text.
+    /// Paint text that has already been layed out in a `Galley`.
-    pub fn add_galley(&self, pos: Pos2, galley: font::Galley, text_style: TextStyle, color: Color) {
+    pub fn galley(&self, pos: Pos2, galley: font::Galley, text_style: TextStyle, color: Color) {
         self.add(PaintCmd::Text {
             pos,
             galley,

egui/src/ui.rs

@@ -106,6 +106,14 @@ impl Ui {
         &self.painter
     }
 
+    /// Create a painter for a sub-region of this Ui.
+    ///
+    /// The clip-rect of the returned `Painter` will be the intersection
+    /// of the given rectangle and the `clip_rect()` of this `Ui`.
+    pub fn painter_at(&self, rect: Rect) -> Painter {
+        self.painter().sub_region(rect)
+    }
+
     /// Use this to paint stuff within this `Ui`.
     pub fn layer(&self) -> Layer {
         self.painter().layer()
@@ -419,6 +427,12 @@ impl Ui {
         self.child_count += 1;
         child_rect
     }
+
+    /// Ask to allocate a certain amount of space and return a Painter for that region.
+    pub fn allocate_canvas(&mut self, size: Vec2) -> Painter {
+        let rect = self.allocate_space(size);
+        self.painter_at(rect)
+    }
 }
 
 /// # Adding widgets

egui/src/widgets.rs

@@ -104,7 +104,7 @@ impl Label {
     pub fn paint_galley(&self, ui: &mut Ui, pos: Pos2, galley: font::Galley) {
         let text_color = self.text_color.unwrap_or_else(|| ui.style().text_color);
         ui.painter()
-            .add_galley(pos, galley, self.text_style, text_color);
+            .galley(pos, galley, self.text_style, text_color);
     }
 }
 
@@ -202,7 +202,7 @@ impl Widget for Hyperlink {
         }
 
         ui.painter()
-            .add_galley(interact.rect.min, galley, text_style, color);
+            .galley(interact.rect.min, galley, text_style, color);
 
         interact
     }
@@ -291,7 +291,7 @@ impl Widget for Button {
         let stroke_color = ui.style().interact(&interact).stroke_color;
         let text_color = text_color.unwrap_or(stroke_color);
         ui.painter()
-            .add_galley(text_cursor, galley, text_style, text_color);
+            .galley(text_cursor, galley, text_style, text_color);
         interact
     }
 }
@@ -368,7 +368,7 @@ impl<'a> Widget for Checkbox<'a> {
 
         let text_color = text_color.unwrap_or(stroke_color);
         ui.painter()
-            .add_galley(text_cursor, galley, text_style, text_color);
+            .galley(text_cursor, galley, text_style, text_color);
         interact
     }
 }
@@ -441,7 +441,7 @@ impl Widget for RadioButton {
         }
 
         let text_color = text_color.unwrap_or(stroke_color);
-        painter.add_galley(text_cursor, galley, text_style, text_color);
+        painter.galley(text_cursor, galley, text_style, text_color);
         interact
     }
 }

egui/src/widgets/slider.rs

@@ -116,7 +116,7 @@ impl<'a> Widget for Slider<'a> {
             if text_on_top {
                 let galley = font.layout_single_line(full_text);
                 let pos = ui.allocate_space(galley.size).min;
-                ui.painter().add_galley(pos, galley, text_style, text_color);
+                ui.painter().galley(pos, galley, text_style, text_color);
                 slider_sans_text.ui(ui)
             } else {
                 ui.columns(2, |columns| {

egui/src/widgets/text_edit.rs

@@ -166,7 +166,7 @@ impl<'t> Widget for TextEdit<'t> {
         }
 
         let text_color = text_color.unwrap_or_else(|| ui.style().text_color);
-        painter.add_galley(interact.rect.min, galley, text_style, text_color);
+        painter.galley(interact.rect.min, galley, text_style, text_color);
         ui.memory().text_edit.insert(id, state);
         interact
     }

example_glium/src/main.rs

@@ -1,6 +1,9 @@
+#![deny(warnings)]
+#![warn(clippy::all)]
+
 use egui_glium::{storage::FileStorage, RunMode};
 
-/// We dervive Deserialize/Serialize so we can persist app state on shutdown.
+/// We derive Deserialize/Serialize so we can persist app state on shutdown.
 #[derive(Default, serde::Deserialize, serde::Serialize)]
 struct MyApp {
     counter: u64,