From bb97f2e98dcf6e2298de3f33acf65befe7ca1732 Mon Sep 17 00:00:00 2001
From: Luke Campagnola <luke.campagnola@gmail.com>
Date: Sun, 28 Feb 2016 20:52:07 -0800
Subject: [PATCH] Switch text anchor when line crosses center of view

---
 pyqtgraph/graphicsItems/InfiniteLine.py | 27 +++++++++++++++++++++++--
 pyqtgraph/graphicsItems/TextItem.py     | 26 ++++++++++--------------
 2 files changed, 36 insertions(+), 17 deletions(-)

diff --git a/pyqtgraph/graphicsItems/InfiniteLine.py b/pyqtgraph/graphicsItems/InfiniteLine.py
index 428f6539..44903ed8 100644
--- a/pyqtgraph/graphicsItems/InfiniteLine.py
+++ b/pyqtgraph/graphicsItems/InfiniteLine.py
@@ -310,20 +310,38 @@ class InfLineLabel(TextItem):
     movable         Bool; if True, then the label can be dragged along the line.
     position        Relative position (0.0-1.0) within the view to position the label
                     along the line.
+    anchors         List of (x,y) pairs giving the text anchor positions that should
+                    be used when the line is moved to one side of the view or the
+                    other. This allows text to switch to the opposite side of the line
+                    as it approaches the edge of the view.
     =============== ==================================================================
     
     All extra keyword arguments are passed to TextItem. A particularly useful
     option here is to use `rotateAxis=(1, 0)`, which will cause the text to
     be automatically rotated parallel to the line.
     """
-    def __init__(self, line, text="", movable=False, position=0.5, **kwds):
+    def __init__(self, line, text="", movable=False, position=0.5, anchors=None, **kwds):
         self.line = line
         self.movable = movable
         self.orthoPos = position  # text will always be placed on the line at a position relative to view bounds
         self.format = text
         self.line.sigPositionChanged.connect(self.valueChanged)
         self._endpoints = (None, None)
-        self.anchors = [(0, 0), (1, 0)]
+        if anchors is None:
+            # automatically pick sensible anchors
+            rax = kwds.get('rotateAxis', None)
+            if rax is not None:
+                if tuple(rax) == (1,0):
+                    anchors = [(0.5, 0), (0.5, 1)]
+                else:
+                    anchors = [(0, 0.5), (1, 0.5)]
+            else:
+                if line.angle % 180 == 0:
+                    anchors = [(0.5, 0), (0.5, 1)]
+                else:
+                    anchors = [(0, 0.5), (1, 0.5)]
+            
+        self.anchors = anchors
         TextItem.__init__(self, **kwds)
         self.setParentItem(line)
         self.valueChanged()
@@ -372,6 +390,11 @@ class InfLineLabel(TextItem):
         pt = pt2 * self.orthoPos + pt1 * (1-self.orthoPos)
         self.setPos(pt)
         
+        # update anchor to keep text visible as it nears the view box edge
+        vr = self.line.viewRect()
+        if vr is not None:
+            self.setAnchor(self.anchors[0 if vr.center().y() < 0 else 1])
+        
     def setVisible(self, v):
         TextItem.setVisible(self, v)
         if v:
diff --git a/pyqtgraph/graphicsItems/TextItem.py b/pyqtgraph/graphicsItems/TextItem.py
index 47d9dac3..dc240929 100644
--- a/pyqtgraph/graphicsItems/TextItem.py
+++ b/pyqtgraph/graphicsItems/TextItem.py
@@ -56,7 +56,6 @@ class TextItem(GraphicsObject):
         self.fill = fn.mkBrush(fill)
         self.border = fn.mkPen(border)
         self.setAngle(angle)
-        #self.textItem.setFlag(self.ItemIgnoresTransformations)  ## This is required to keep the text unscaled inside the viewport
 
     def setText(self, text, color=(200,200,200)):
         """
@@ -67,14 +66,7 @@ class TextItem(GraphicsObject):
         color = fn.mkColor(color)
         self.textItem.setDefaultTextColor(color)
         self.textItem.setPlainText(text)
-        self.updateText()
-        #html = '<span style="color: #%s; text-align: center;">%s</span>' % (color, text)
-        #self.setHtml(html)
-        
-    def updateAnchor(self):
-        pass
-        #self.resetTransform()
-        #self.translate(0, 20)
+        self.updateTextPos()
         
     def setPlainText(self, *args):
         """
@@ -83,7 +75,7 @@ class TextItem(GraphicsObject):
         See QtGui.QGraphicsTextItem.setPlainText().
         """
         self.textItem.setPlainText(*args)
-        self.updateText()
+        self.updateTextPos()
         
     def setHtml(self, *args):
         """
@@ -92,7 +84,7 @@ class TextItem(GraphicsObject):
         See QtGui.QGraphicsTextItem.setHtml().
         """
         self.textItem.setHtml(*args)
-        self.updateText()
+        self.updateTextPos()
         
     def setTextWidth(self, *args):
         """
@@ -104,7 +96,7 @@ class TextItem(GraphicsObject):
         See QtGui.QGraphicsTextItem.setTextWidth().
         """
         self.textItem.setTextWidth(*args)
-        self.updateText()
+        self.updateTextPos()
         
     def setFont(self, *args):
         """
@@ -113,13 +105,17 @@ class TextItem(GraphicsObject):
         See QtGui.QGraphicsTextItem.setFont().
         """
         self.textItem.setFont(*args)
-        self.updateText()
+        self.updateTextPos()
         
     def setAngle(self, angle):
         self.angle = angle
         self.updateTransform()
         
-    def updateText(self):
+    def setAnchor(self, anchor):
+        self.anchor = Point(anchor)
+        self.updateTextPos()
+        
+    def updateTextPos(self):
         # update text position to obey anchor
         r = self.textItem.boundingRect()
         tl = self.textItem.mapToParent(r.topLeft())
@@ -184,6 +180,6 @@ class TextItem(GraphicsObject):
         
         self._lastTransform = pt
         
-        self.updateText()
+        self.updateTextPos()
 
         
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