silx.gui.plot.PlotWidget: Added support of line style defined as (offset, (dash pattern))

src/silx/gui/plot/LegendSelector.py

@@ -252,7 +252,7 @@ def setData(self, modelIndex, value, role):
             elif role == self.iconLineWidthRole:
                 item[1]["linewidth"] = int(value)
             elif role == self.iconLineStyleRole:
-                item[1]["linestyle"] = str(value)
+                item[1]["linestyle"] = value
             elif role == self.iconSymbolRole:
                 item[1]["symbol"] = str(value)
             elif role == qt.Qt.CheckStateRole:
@@ -674,7 +674,7 @@ def _handleMouseClick(self, modelIndex):
             "legend": str(modelIndex.data(qt.Qt.DisplayRole)),
             "icon": {
                 "linewidth": str(modelIndex.data(LegendModel.iconLineWidthRole)),
-                "linestyle": str(modelIndex.data(LegendModel.iconLineStyleRole)),
+                "linestyle": modelIndex.data(LegendModel.iconLineStyleRole),
                 "symbol": str(modelIndex.data(LegendModel.iconSymbolRole)),
             },
             "selected": modelIndex.data(qt.Qt.CheckStateRole),

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

@@ -126,13 +126,14 @@ def addCurve(
             - 's' square
 
         :param float linewidth: The width of the curve in pixels
-        :param str linestyle: Type of line::
+        :param linestyle: Type of line::
 
             - ' ' or ''  no line
             - '-'  solid line
             - '--' dashed line
             - '-.' dash-dot line
             - ':'  dotted line
+            - (offset, (dash pattern))
 
         :param str yaxis: The Y axis this curve belongs to in: 'left', 'right'
         :param xerror: Values with the uncertainties on the x values
@@ -190,7 +191,7 @@ def addShape(
         :param str color: Color of the item
         :param bool fill: True to fill the shape
         :param bool overlay: True if item is an overlay, False otherwise
-        :param str linestyle: Style of the line.
+        :param linestyle: Style of the line.
             Only relevant for line markers where X or Y is None.
             Value in:
 
@@ -199,6 +200,7 @@ def addShape(
             - '--' dashed line
             - '-.' dash-dot line
             - ':'  dotted line
+            - (offset, (dash pattern))
         :param float linewidth: Width of the line.
             Only relevant for line markers where X or Y is None.
         :param str gapcolor: Background color of the line, e.g., 'blue', 'b',
@@ -214,7 +216,7 @@ def addMarker(
         text: str | None,
         color: str,
         symbol: str | None,
-        linestyle: str,
+        linestyle: str | tuple[float, tuple[float, ...] | None],
         linewidth: float,
         constraint: Callable[[float, float], tuple[float, float]] | None,
         yaxis: str,
@@ -250,6 +252,7 @@ def addMarker(
             - '--' dashed line
             - '-.' dash-dot line
             - ':'  dotted line
+            - (offset, (dash pattern))
         :param linewidth: Width of the line.
             Only relevant for line markers where X or Y is None.
         :param constraint: A function filtering marker displacement by
@@ -300,8 +303,9 @@ def setGraphCursor(self, flag, color, linewidth, linestyle):
                 - '--' dashed line
                 - '-.' dash-dot line
                 - ':' dotted line
+                - (offset, (dash pattern))
 
-        :type linestyle: None or one of the predefined styles.
+        :type linestyle: None, one of the predefined styles or (offset, (dash pattern)).
         """
         pass
 

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

@@ -1636,6 +1636,10 @@ def draw(self):
 
         self.updateZOrder()
 
+        if not qt_inspect.isValid(self):
+            _logger.info("draw requested but widget no longer exists")
+            return
+
         # Starting with mpl 2.1.0, toggling autoscale raises a ValueError
         # in some situations. See #1081, #1136, #1163,
         if self._matplotlibVersion >= Version("2.0.0"):

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

@@ -58,7 +58,17 @@
 
 class _ShapeItem(dict):
     def __init__(
-        self, x, y, shape, color, fill, overlay, linewidth, dashpattern, gapcolor
+        self,
+        x,
+        y,
+        shape,
+        color,
+        fill,
+        overlay,
+        linewidth,
+        dashoffset,
+        dashpattern,
+        gapcolor,
     ):
         super(_ShapeItem, self).__init__()
 
@@ -85,6 +95,7 @@ def __init__(
                 "x": x,
                 "y": y,
                 "linewidth": linewidth,
+                "dashoffset": dashoffset,
                 "dashpattern": dashpattern,
                 "gapcolor": gapcolor,
             }
@@ -100,6 +111,7 @@ def __init__(
         color,
         symbol,
         linewidth,
+        dashoffset,
         dashpattern,
         constraint,
         yaxis,
@@ -125,6 +137,7 @@ def __init__(
                 "constraint": constraint if isConstraint else None,
                 "symbol": symbol,
                 "linewidth": linewidth,
+                "dashoffset": dashoffset,
                 "dashpattern": dashpattern,
                 "yaxis": yaxis,
                 "font": font,
@@ -588,6 +601,7 @@ def _renderItems(self, overlay=False):
                             color=item["color"],
                             gapColor=item["gapcolor"],
                             width=item["linewidth"],
+                            dashOffset=item["dashoffset"],
                             dashPattern=item["dashpattern"],
                         )
                         context.matrix = self.matScreenProj
@@ -638,6 +652,7 @@ def _renderItems(self, overlay=False):
                             (pixelPos[1], pixelPos[1]),
                             color=color,
                             width=item["linewidth"],
+                            dashOffset=item["dashoffset"],
                             dashPattern=item["dashpattern"],
                         )
                         context.matrix = self.matScreenProj
@@ -671,6 +686,7 @@ def _renderItems(self, overlay=False):
                             (0, height),
                             color=color,
                             width=item["linewidth"],
+                            dashOffset=item["dashoffset"],
                             dashPattern=item["dashpattern"],
                         )
                         context.matrix = self.matScreenProj
@@ -859,21 +875,37 @@ def _castArrayTo(v):
         else:
             raise ValueError("Unsupported data type")
 
-    _DASH_PATTERNS = {  # Convert from linestyle to dash pattern
-        "": None,
-        " ": None,
-        "-": (),
-        "--": (3.7, 1.6, 3.7, 1.6),
-        "-.": (6.4, 1.6, 1, 1.6),
-        ":": (1, 1.65, 1, 1.65),
-        None: None,
+    _DASH_PATTERNS = {
+        "": (0.0, None),
+        " ": (0.0, None),
+        "-": (0.0, ()),
+        "--": (0.0, (3.7, 1.6, 3.7, 1.6)),
+        "-.": (0.0, (6.4, 1.6, 1, 1.6)),
+        ":": (0.0, (1, 1.65, 1, 1.65)),
+        None: (0.0, None),
     }
+    """Convert from linestyle to (offset, (dash pattern))
 
-    def _lineStyleToDashPattern(
-        self, style: str | None
-    ) -> tuple[float, float, float, float] | tuple[()] | None:
-        """Convert a linestyle to its corresponding dash pattern"""
-        return self._DASH_PATTERNS[style]
+    Note: dash pattern internal convention differs from matplotlib:
+    - None: no line at all
+    - (): "solid" line
+    """
+
+    def _lineStyleToDashOffsetPattern(
+        self, style
+    ) -> tuple[float, tuple[float, float, float, float] | tuple[()] | None]:
+        """Convert a linestyle to its corresponding offset and dash pattern"""
+        if style is None or isinstance(style, str):
+            return self._DASH_PATTERNS[style]
+
+        # (offset, (dash pattern)) case
+        offset, pattern = style
+        if pattern is None:
+            # Convert from matplotlib to internal representation of solid
+            pattern = ()
+        if len(pattern) == 2:
+            pattern = pattern * 2
+        return offset, pattern
 
     def addCurve(
         self,
@@ -994,6 +1026,7 @@ def addCurve(
         if fill is True:
             fillColor = color
 
+        dashoffset, dashpattern = self._lineStyleToDashOffsetPattern(linestyle)
         curve = glutils.GLPlotCurve2D(
             x,
             y,
@@ -1003,7 +1036,8 @@ def addCurve(
             lineColor=color,
             lineGapColor=gapcolor,
             lineWidth=linewidth,
-            lineDashPattern=self._lineStyleToDashPattern(linestyle),
+            lineDashOffset=dashoffset,
+            lineDashPattern=dashpattern,
             marker=symbol,
             markerColor=color,
             markerSize=symbolsize,
@@ -1108,9 +1142,18 @@ def addShape(
         if self._plotFrame.yAxis.isLog and y.min() <= 0.0:
             raise RuntimeError("Cannot add item with Y <= 0 with Y axis log scale")
 
-        dashpattern = self._lineStyleToDashPattern(linestyle)
+        dashoffset, dashpattern = self._lineStyleToDashOffsetPattern(linestyle)
         return _ShapeItem(
-            x, y, shape, color, fill, overlay, linewidth, dashpattern, gapcolor
+            x,
+            y,
+            shape,
+            color,
+            fill,
+            overlay,
+            linewidth,
+            dashoffset,
+            dashpattern,
+            gapcolor,
         )
 
     def addMarker(
@@ -1128,14 +1171,15 @@ def addMarker(
         bgcolor: RGBAColorType | None,
     ):
         font = qt.QApplication.instance().font() if font is None else font
-        dashpattern = self._lineStyleToDashPattern(linestyle)
+        dashoffset, dashpattern = self._lineStyleToDashOffsetPattern(linestyle)
         return _MarkerItem(
             x,
             y,
             text,
             color,
             symbol,
             linewidth,
+            dashoffset,
             dashpattern,
             constraint,
             yaxis,

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

@@ -292,6 +292,8 @@ class GLLines2D(object):
         "unscaled" dash pattern as 4 lengths in points (dash1, gap1, dash2, gap2).
         This pattern is scaled with the line width.
         Set to () to draw solid lines (default), and to None to disable rendering.
+    :param float dashOffset: The offset in points the patterns starts at.
+        The offset is scaled with the line width.
     :param drawMode: OpenGL drawing mode
     :param List[float] offset: Translation of coordinates (ox, oy)
     """
@@ -353,13 +355,14 @@ class GLLines2D(object):
         /* Dashes: [0, x], [y, z]
            Dash period: w */
         uniform vec4 dash;
+        uniform float dashOffset;
         uniform vec4 gapColor;
 
         varying float vDist;
         varying vec4 vColor;
 
         void main(void) {
-            float dist = mod(vDist, dash.w);
+            float dist = mod(vDist + dashOffset, dash.w);
             if ((dist > dash.x && dist < dash.y) || dist > dash.z) {
                 if (gapColor.a == 0.) {
                     discard;  // Discard full transparent bg color
@@ -383,6 +386,7 @@ def __init__(
         color=(0.0, 0.0, 0.0, 1.0),
         gapColor=None,
         width=1,
+        dashOffset=0.0,
         dashPattern=(),
         drawMode=None,
         offset=(0.0, 0.0),
@@ -416,6 +420,7 @@ def __init__(
         self.gapColor = gapColor
         self.width = width
         self.dashPattern = dashPattern
+        self.dashOffset = dashOffset
         self.offset = offset
 
         self._drawMode = drawMode if drawMode is not None else gl.GL_LINE_STRIP
@@ -447,6 +452,7 @@ def render(self, context):
                 offset * scale for offset in numpy.cumsum(self.dashPattern)
             )
             gl.glUniform4f(program.uniforms["dash"], *dashOffsets)
+            gl.glUniform1f(program.uniforms["dashOffset"], self.dashOffset * scale)
 
             if self.gapColor is None:
                 # Use fully transparent color which gets discarded in shader
@@ -1188,6 +1194,7 @@ def __init__(
         lineColor=(0.0, 0.0, 0.0, 1.0),
         lineGapColor=None,
         lineWidth=1,
+        lineDashOffset=0.0,
         lineDashPattern=(),
         marker=SQUARE,
         markerColor=(0.0, 0.0, 0.0, 1.0),
@@ -1278,6 +1285,7 @@ def deduce_baseline(baseline):
         self.lines.color = lineColor
         self.lines.gapColor = lineGapColor
         self.lines.width = lineWidth
+        self.lines.dashOffset = lineDashOffset
         self.lines.dashPattern = lineDashPattern
         self.lines.offset = self.offset
 
@@ -1305,6 +1313,8 @@ def deduce_baseline(baseline):
 
     lineWidth = _proxyProperty(("lines", "width"))
 
+    lineDashOffset = _proxyProperty(("lines", "dashOffset"))
+
     lineDashPattern = _proxyProperty(("lines", "dashPattern"))
 
     marker = _proxyProperty(("points", "marker"))