Cleanup TextBox implementation.

- Reuse a single Text instance to measure cursor width and display text,
  instead of creating a new one every time the text is edited.
- Likewise, reuse a single LineCollection for the cursor (I guess a
  Line2D would be more efficient but I'm too lazy to go through the API
  change here).  Also, putting the LineCollection in pixel coordinates
  (`transforms=IdentityTransform()`) makes things much simpler.
- Auto-sync `.text` and the contents of the text field.
- `._lastcolor` is just the current axes color.
- Misc. cleanups.

Author: anntzer

lib/matplotlib/widgets.py

@@ -190,8 +190,6 @@ def __init__(self, ax, label, image=None,
         self.color = color
         self.hovercolor = hovercolor
 
-        self._lastcolor = color
-
     def _click(self, event):
         if (self.ignore(event)
                 or event.inaxes != self.ax
@@ -706,76 +704,58 @@ def __init__(self, ax, label, initial='',
 
         self.DIST_FROM_LEFT = .05
 
-        self.text = initial
-        self.label = ax.text(-label_pad, 0.5, label,
-                             verticalalignment='center',
-                             horizontalalignment='right',
-                             transform=ax.transAxes)
-        self.text_disp = self._make_text_disp(self.text)
+        self.label = ax.text(
+            -label_pad, 0.5, label, transform=ax.transAxes,
+            verticalalignment='center', horizontalalignment='right')
+        self.text_disp = self.ax.text(
+            self.DIST_FROM_LEFT, 0.5, initial, transform=self.ax.transAxes,
+            verticalalignment='center', horizontalalignment='left')
 
         self.cnt = 0
         self.change_observers = {}
         self.submit_observers = {}
 
-        # If these lines are removed, the cursor won't appear the first
-        # time the box is clicked:
-        self.ax.set_xlim(0, 1)
-        self.ax.set_ylim(0, 1)
+        ax.set(
+            xlim=(0, 1), ylim=(0, 1),  # s.t. cursor appears from first click.
+            navigate=False, facecolor=color,
+            xticks=[], yticks=[])
 
         self.cursor_index = 0
 
-        # Because this is initialized, _render_cursor
-        # can assume that cursor exists.
-        self.cursor = self.ax.vlines(0, 0, 0)
-        self.cursor.set_visible(False)
+        self.cursor = ax.vlines(0, 0, 0, visible=False,
+                                transform=mpl.transforms.IdentityTransform())
 
         self.connect_event('button_press_event', self._click)
         self.connect_event('button_release_event', self._release)
         self.connect_event('motion_notify_event', self._motion)
         self.connect_event('key_press_event', self._keypress)
         self.connect_event('resize_event', self._resize)
-        ax.set_navigate(False)
-        ax.set_facecolor(color)
-        ax.set_xticks([])
-        ax.set_yticks([])
+
         self.color = color
         self.hovercolor = hovercolor
 
-        self._lastcolor = color
-
         self.capturekeystrokes = False
 
-    def _make_text_disp(self, string):
-        return self.ax.text(self.DIST_FROM_LEFT, 0.5, string,
-                            verticalalignment='center',
-                            horizontalalignment='left',
-                            transform=self.ax.transAxes)
+    @property
+    def text(self):
+        return self.text_disp.get_text()
 
     def _rendercursor(self):
         # this is a hack to figure out where the cursor should go.
         # we draw the text up to where the cursor should go, measure
         # and save its dimensions, draw the real text, then put the cursor
         # at the saved dimensions
 
-        widthtext = self.text[:self.cursor_index]
-        no_text = False
-        if widthtext in ["", " ", "  "]:
-            no_text = widthtext == ""
-            widthtext = ","
-
-        wt_disp = self._make_text_disp(widthtext)
-
-        self.ax.figure.canvas.draw()
-        bb = wt_disp.get_window_extent()
-        inv = self.ax.transData.inverted()
-        bb = inv.transform(bb)
-        wt_disp.set_visible(False)
-        if no_text:
-            bb[1, 0] = bb[0, 0]
-        # hack done
-        self.cursor.set_visible(False)
+        text = self.text_disp.get_text()  # Save value before overwriting it.
+        widthtext = text[:self.cursor_index]
+        self.text_disp.set_text(widthtext or ",")
+        bb = self.text_disp.get_window_extent()
+        if not widthtext:  # Use the comma for the height, but keep width to 0.
+            bb.x1 = bb.x0
+        self.cursor.set(
+            segments=[[(bb.x1, bb.y0), (bb.x1, bb.y1)]], visible=True)
+        self.text_disp.set_text(text)
 
-        self.cursor = self.ax.vlines(bb[1, 0], bb[0, 1], bb[1, 1])
         self.ax.figure.canvas.draw()
 
     def _notify_submit_observers(self):
@@ -795,33 +775,31 @@ def _keypress(self, event):
             return
         if self.capturekeystrokes:
             key = event.key
-
+            text = self.text
             if len(key) == 1:
-                self.text = (self.text[:self.cursor_index] + key +
-                             self.text[self.cursor_index:])
+                text = (text[:self.cursor_index] + key +
+                        text[self.cursor_index:])
                 self.cursor_index += 1
             elif key == "right":
-                if self.cursor_index != len(self.text):
+                if self.cursor_index != len(text):
                     self.cursor_index += 1
             elif key == "left":
                 if self.cursor_index != 0:
                     self.cursor_index -= 1
             elif key == "home":
                 self.cursor_index = 0
             elif key == "end":
-                self.cursor_index = len(self.text)
+                self.cursor_index = len(text)
             elif key == "backspace":
                 if self.cursor_index != 0:
-                    self.text = (self.text[:self.cursor_index - 1] +
-                                 self.text[self.cursor_index:])
+                    text = (text[:self.cursor_index - 1] +
+                            text[self.cursor_index:])
                     self.cursor_index -= 1
             elif key == "delete":
                 if self.cursor_index != len(self.text):
-                    self.text = (self.text[:self.cursor_index] +
-                                 self.text[self.cursor_index + 1:])
-
-            self.text_disp.remove()
-            self.text_disp = self._make_text_disp(self.text)
+                    text = (text[:self.cursor_index] +
+                            text[self.cursor_index + 1:])
+            self.text_disp.set_text(text)
             self._rendercursor()
             self._notify_change_observers()
             if key == "enter":
@@ -831,9 +809,7 @@ def set_val(self, val):
         newval = str(val)
         if self.text == newval:
             return
-        self.text = newval
-        self.text_disp.remove()
-        self.text_disp = self._make_text_disp(self.text)
+        self.text_disp.set_text(newval)
         self._rendercursor()
         self._notify_change_observers()
         self._notify_submit_observers()
@@ -885,23 +861,8 @@ def position_cursor(self, x):
             self.cursor_index = 0
         else:
             bb = self.text_disp.get_window_extent()
-
-            trans = self.ax.transData
-            inv = self.ax.transData.inverted()
-            bb = trans.transform(inv.transform(bb))
-
-            text_start = bb[0, 0]
-            text_end = bb[1, 0]
-
-            ratio = (x - text_start) / (text_end - text_start)
-
-            if ratio < 0:
-                ratio = 0
-            if ratio > 1:
-                ratio = 1
-
+            ratio = np.clip((x - bb.x0) / bb.width, 0, 1)
             self.cursor_index = int(len(self.text) * ratio)
-
         self._rendercursor()
 
     def _click(self, event):
@@ -924,13 +885,9 @@ def _resize(self, event):
     def _motion(self, event):
         if self.ignore(event):
             return
-        if event.inaxes == self.ax:
-            c = self.hovercolor
-        else:
-            c = self.color
-        if c != self._lastcolor:
+        c = self.hovercolor if event.inaxes == self.ax else self.color
+        if c != self.ax.get_facecolor():
             self.ax.set_facecolor(c)
-            self._lastcolor = c
             if self.drawon:
                 self.ax.figure.canvas.draw()