Merge pull request #4034 from t20100/gl-text-padding

silx.gui.plot.PlotWidget: Improved text background rendering for OpenGL backend

src/silx/gui/plot/backends/BackendOpenGL.py

@@ -227,6 +227,8 @@ class BackendOpenGL(BackendBase.BackendBase, glu.OpenGLWidget):
     So, the caller should not modify these arrays afterwards.
     """
 
+    _TEXT_MARKER_PADDING = 4
+
     def __init__(self, plot, parent=None, f=qt.Qt.Widget):
         glu.OpenGLWidget.__init__(
             self,
@@ -645,6 +647,7 @@ def _renderItems(self, overlay=False):
                                 align=glutils.RIGHT,
                                 valign=glutils.BOTTOM,
                                 devicePixelRatio=self.getDevicePixelRatio(),
+                                padding=self._TEXT_MARKER_PADDING,
                             )
                             labels.append(label)
 
@@ -679,6 +682,7 @@ def _renderItems(self, overlay=False):
                                 align=glutils.LEFT,
                                 valign=glutils.TOP,
                                 devicePixelRatio=self.getDevicePixelRatio(),
+                                padding=self._TEXT_MARKER_PADDING,
                             )
                             labels.append(label)
 
@@ -722,6 +726,7 @@ def _renderItems(self, overlay=False):
                             align=glutils.LEFT,
                             valign=valign,
                             devicePixelRatio=self.getDevicePixelRatio(),
+                            padding=self._TEXT_MARKER_PADDING,
                         )
                         labels.append(label)
 
@@ -907,7 +912,7 @@ def _lineStyleToDashOffsetPattern(
             pattern = ()
         if len(pattern) == 2:
             pattern = pattern * 2
-        return offset, pattern
+        return float(offset), tuple(float(v) for v in pattern)
 
     def addCurve(
         self,
@@ -1162,6 +1167,7 @@ def getDefaultFont(self):
         """Returns the default font, used by raw markers and axes labels"""
         if self._defaultFont is None:
             from matplotlib.font_manager import findfont, FontProperties
+
             font_filename = findfont(FontProperties(family=["sans-serif"]))
             _logger.debug("Load font from mpl: %s", font_filename)
             id = qt.QFontDatabase.addApplicationFont(font_filename)

src/silx/gui/plot/backends/glutils/GLText.py

@@ -116,15 +116,15 @@ class Text2D:
     varying vec2 vCoords;
 
     void main(void) {
-        gl_FragColor = mix(bgColor, color, texture2D(texText, vCoords).r);
+        if (vCoords.x < 0.0 || vCoords.x > 1.0 || vCoords.y < 0.0 || vCoords.y > 1.0) {
+            gl_FragColor = bgColor;
+        } else {
+            gl_FragColor = mix(bgColor, color, texture2D(texText, vCoords).r);
+        }
     }
     """,
     }
 
-    _TEX_COORDS = numpy.array(
-        ((0.0, 0.0), (1.0, 0.0), (0.0, 1.0), (1.0, 1.0)), dtype=numpy.float32
-    ).ravel()
-
     _program = Program(_SHADERS["vertex"], _SHADERS["fragment"], attrib0="position")
 
     # Discard texture objects when removed from the cache
@@ -146,11 +146,13 @@ def __init__(
         valign: str = BASELINE,
         rotate: float = 0.0,
         devicePixelRatio: float = 1.0,
+        padding: int = 0,
     ):
         self.devicePixelRatio = devicePixelRatio
         self.font = font
         self._vertices = None
         self._text = text
+        self._padding = padding
         self.x = x
         self.y = y
         self.color = color
@@ -204,6 +206,10 @@ def _getTexture(self) -> tuple[Texture, int]:
     def text(self) -> str:
         return self._text
 
+    @property
+    def padding(self) -> int:
+        return self._padding
+
     @property
     def size(self) -> tuple[int, int]:
         textureKey = self._textureKey()
@@ -282,17 +288,31 @@ def render(self, matrix: numpy.ndarray):
             bgColor = self.color[0], self.color[1], self.color[2], 0.0
         gl.glUniform4f(prog.uniforms["bgColor"], *bgColor)
 
-        vertices = self.getVertices(offset, texture.shape)
+        paddingOffset = max(0, int(self.padding * self.devicePixelRatio))
+        height, width = texture.shape
+        vertices = self.getVertices(
+            offset, (height + 2 * paddingOffset, width + 2 * paddingOffset)
+        )
 
         posAttrib = prog.attributes["position"]
         gl.glEnableVertexAttribArray(posAttrib)
         gl.glVertexAttribPointer(posAttrib, 2, gl.GL_FLOAT, gl.GL_FALSE, 0, vertices)
 
+        xoffset = paddingOffset / width
+        yoffset = paddingOffset / height
+        texCoords = numpy.array(
+            (
+                (-xoffset, -yoffset),
+                (1.0 + xoffset, -yoffset),
+                (-xoffset, 1.0 + yoffset),
+                (1.0 + xoffset, 1.0 + yoffset),
+            ),
+            dtype=numpy.float32,
+        ).ravel()
+
         texAttrib = prog.attributes["texCoords"]
         gl.glEnableVertexAttribArray(texAttrib)
-        gl.glVertexAttribPointer(
-            texAttrib, 2, gl.GL_FLOAT, gl.GL_FALSE, 0, self._TEX_COORDS
-        )
+        gl.glVertexAttribPointer(texAttrib, 2, gl.GL_FLOAT, gl.GL_FALSE, 0, texCoords)
 
         with texture:
             gl.glDrawArrays(gl.GL_TRIANGLE_STRIP, 0, 4)