Add HPos and VPos::Default to allow the user to override axes label anchors

Author: VincentFoulon80

plotters-backend/src/lib.rs

@@ -236,12 +236,12 @@ pub trait DrawingBackend: Sized {
         let width = (max_x - min_x) as i32;
         let height = (max_y - min_y) as i32;
         let dx = match style.anchor().h_pos {
-            HPos::Left => 0,
+            HPos::Left | HPos::Default => 0,
             HPos::Right => -width,
             HPos::Center => -width / 2,
         };
         let dy = match style.anchor().v_pos {
-            VPos::Top => 0,
+            VPos::Top | VPos::Default => 0,
             VPos::Center => -height / 2,
             VPos::Bottom => -height,
         };

plotters-backend/src/text.rs

@@ -62,6 +62,9 @@ pub mod text_anchor {
     /// The horizontal position of the anchor point relative to the text.
     #[derive(Clone, Copy)]
     pub enum HPos {
+        /// Default value (Left), except chart axes that might provide a different pos.
+        /// Use another variant to override the default positionning
+        Default,
         /// Anchor point is on the left side of the text
         Left,
         /// Anchor point is on the right side of the text
@@ -73,6 +76,9 @@ pub mod text_anchor {
     /// The vertical position of the anchor point relative to the text.
     #[derive(Clone, Copy)]
     pub enum VPos {
+        /// Default value (Top), except chart axes that might provide a different pos
+        /// Use another variant to override the default positionning
+        Default,
         /// Anchor point is on the top of the text
         Top,
         /// Anchor point is in the vertical center of the text
@@ -117,8 +123,8 @@ pub mod text_anchor {
         /// ```
         pub fn default() -> Self {
             Pos {
-                h_pos: HPos::Left,
-                v_pos: VPos::Top,
+                h_pos: HPos::Default,
+                v_pos: VPos::Default,
             }
         }
     }

plotters-svg/src/svg.rs

@@ -395,13 +395,13 @@ impl<'a> DrawingBackend for SVGBackend<'a> {
 
         let (x0, y0) = pos;
         let text_anchor = match style.anchor().h_pos {
-            HPos::Left => "start",
+            HPos::Left | HPos::Default => "start",
             HPos::Right => "end",
             HPos::Center => "middle",
         };
 
         let dy = match style.anchor().v_pos {
-            VPos::Top => "0.76em",
+            VPos::Top | VPos::Default => "0.76em",
             VPos::Center => "0.5ex",
             VPos::Bottom => "-0.5ex",
         };

plotters/examples/console.rs

@@ -132,12 +132,12 @@ impl DrawingBackend for TextDrawingBackend {
         let (width, height) = self.estimate_text_size(text, style)?;
         let (width, height) = (width as i32, height as i32);
         let dx = match style.anchor().h_pos {
-            HPos::Left => 0,
+            HPos::Left | HPos::Default => 0,
             HPos::Right => -width,
             HPos::Center => -width / 2,
         };
         let dy = match style.anchor().v_pos {
-            VPos::Top => 0,
+            VPos::Top | VPos::Default => 0,
             VPos::Center => -height / 2,
             VPos::Bottom => -height,
         };

plotters/src/chart/context/cartesian2d/draw_impl.rs

@@ -250,6 +250,16 @@ impl<'a, DB: DrawingBackend, X: Ranged, Y: Ranged> ChartContext<'a, DB, Cartesia
                 (cx, cy + label_offset)
             };
 
+            let h_pos = if matches!(label_style.pos.h_pos, HPos::Default) {
+                h_pos
+            } else {
+                label_style.pos.h_pos
+            };
+            let v_pos = if matches!(label_style.pos.v_pos, VPos::Default) {
+                v_pos
+            } else {
+                label_style.pos.v_pos
+            };
             let label_style = &label_style.pos(Pos::new(h_pos, v_pos));
             area.draw_text(t, label_style, (text_x, text_y))?;