Fix issue #186

Fix the code that may map the vlaue out of drawing area.

However, the root cause of this issue is the ambiguity of the backend
coordinate system. To properly address this issue, we need to clean up
the backend coordinate system ambiguities in the future.

Author: 38

plotters/src/chart/builder.rs

@@ -411,7 +411,9 @@ impl<'a, 'b, DB: DrawingBackend> ChartBuilder<'a, 'b, DB> {
         }
 
         let mut pixel_range = drawing_area.get_pixel_range();
-        pixel_range.1 = (pixel_range.1.end - 1)..(pixel_range.1.start - 1);
+        pixel_range.0.end -= 1;
+        pixel_range.1.end -= 1;
+        pixel_range.1 = pixel_range.1.end..pixel_range.1.start;
 
         let mut x_label_area = [None, None];
         let mut y_label_area = [None, None];

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

@@ -78,9 +78,8 @@ impl<'a, DB: DrawingBackend, X: Ranged, Y: Ranged> ChartContext<'a, DB, Cartesia
             self.drawing_area.get_y_axis_pixel_range()
         };
 
-        /* At this point, the coordinate system tells us the pixel range
-         * after the translation.
-         * However, we need to use the logic coordinate system for drawing. */
+        // At this point, the coordinate system tells us the pixel range after the translation.
+        // However, we need to use the logic coordinate system for drawing.
         if orientation.0 == 0 {
             axis_range.start -= x0;
             axis_range.end -= x0;

plotters/src/coord/ranged1d/mod.rs

@@ -213,7 +213,7 @@ pub trait Ranged {
         if limit.0 < limit.1 {
             limit.0..limit.1
         } else {
-            (limit.1 + 1)..(limit.0 + 1)
+            limit.1..limit.0
         }
     }
 }

plotters/src/coord/ranged1d/types/numeric.rs

@@ -87,7 +87,11 @@ macro_rules! make_numeric_coord {
                     return limit.1;
                 }
 
-                return limit.0 + (actual_length as f64 * logic_length + 1e-3).floor() as i32;
+                if actual_length > 0 {
+                    return limit.0 + (actual_length as f64 * logic_length + 1e-3).floor() as i32;
+                } else {
+                    return limit.0 + (actual_length as f64 * logic_length - 1e-3).ceil() as i32;
+                }
             }
             fn key_points<Hint: KeyPointHint>(&self, hint: Hint) -> Vec<$type> {
                 $key_points((self.0, self.1), hint.max_num_points())
@@ -165,7 +169,7 @@ macro_rules! gen_key_points_comp {
             }
 
             let mut ret = vec![];
-            // In some extreme cases, left might be too big, so that (left + scale) - left == 0 due to 
+            // In some extreme cases, left might be too big, so that (left + scale) - left == 0 due to
             // floating point error.
             // In this case, we may loop forever. To avoid this, we need to use two variables to store
             // the current left value. So we need keep a left_base and a left_relative.
@@ -180,7 +184,8 @@ macro_rules! gen_key_points_comp {
             let mut left_relative = left - left_base;
             let right = range.1 - rem_euclid(range.1, scale);
             while (right - left_relative - left_base) >= -std::f64::EPSILON {
-                let new_left_relative = (left_relative / value_granularity).round() * value_granularity;
+                let new_left_relative =
+                    (left_relative / value_granularity).round() * value_granularity;
                 if new_left_relative < 0.0 {
                     left_relative += value_granularity;
                 }