Add non-linear scale warning to image drawing methods

This is related to #36

Author: PierreRaybaut

plotpy/items/image/base.py

@@ -14,7 +14,7 @@
 from guidata.utils.misc import assert_interfaces_valid
 from qtpy import QtCore as QC
 from qtpy import QtGui as QG
-from qwt import QwtPlotItem
+from qwt import QwtLinearScaleEngine, QwtPlotItem
 
 from plotpy import io
 from plotpy._scaler import (
@@ -55,6 +55,7 @@
     from qtpy.QtGui import QColor, QPainter
 
     from plotpy.interfaces import IItemType
+    from plotpy.plot import BasePlot
     from plotpy.styles.base import ItemParameters
     from plotpy.widgets.colormap.widget import EditableColormap
 
@@ -582,6 +583,29 @@ def draw_border(
         """
         self.border_rect.draw(painter, xMap, yMap, canvasRect)
 
+    def warn_if_non_linear_scale(self, painter: QPainter, canvasRect: QRectF) -> bool:
+        """Warn if non-linear scale
+
+        Args:
+            painter: Painter
+            canvasRect: Canvas rectangle
+
+        Returns:
+            True if non-linear scale
+        """
+        plot: BasePlot = self.plot()
+        if not isinstance(
+            plot.axisScaleEngine(plot.X_BOTTOM), QwtLinearScaleEngine
+        ) or not isinstance(plot.axisScaleEngine(plot.Y_LEFT), QwtLinearScaleEngine):
+            painter.setPen(QC.Qt.red)
+            painter.drawText(
+                canvasRect,
+                QC.Qt.AlignCenter,
+                _("Non-linear scales are not supported for image items"),
+            )
+            return True
+        return False
+
     def draw_image(
         self,
         painter: QPainter,
@@ -601,6 +625,8 @@ def draw_image(
             xMap: X axis scale map
             yMap: Y axis scale map
         """
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
         dest = _scale_rect(
             self.data, src_rect, self._offscreen, dst_rect, self.lut, self.interpolate
         )

plotpy/items/image/image_items.py

@@ -376,6 +376,9 @@ def draw_image(
         """
         if self.data is None:
             return
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
+
         src2 = self._rescale_src_rect(src_rect)
         dst_rect = tuple([int(i) for i in dst_rect])
 
@@ -651,6 +654,8 @@ def draw_image(
             xMap: X axis scale map
             yMap: Y axis scale map
         """
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
         xytr = self.x, self.y, src_rect
         dst_rect = tuple([int(i) for i in dst_rect])
         dest = _scale_xy(

plotpy/items/image/misc.py

@@ -169,6 +169,8 @@ def draw_image(
             xMap: X axis scale map
             yMap: Y axis scale map
         """
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
         self._offscreen[...] = np.uint32(0)
         dest = _scale_quads(
             self.X,
@@ -294,6 +296,8 @@ def draw_image(
             xMap: X axis scale map
             yMap: Y axis scale map
         """
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
         computation = self.histparam.computation
         i1, j1, i2, j2 = src_rect
 

plotpy/items/image/transform.py

@@ -257,6 +257,8 @@ def draw_image(
             xMap: X axis scale map
             yMap: Y axis scale map
         """
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
         W = canvasRect.width()
         H = canvasRect.height()
         if W <= 1 or H <= 1:

plotpy/tests/items/test_mandelbrot.py

@@ -47,6 +47,8 @@ def __init__(self, xmin, xmax, ymin, ymax):
 
     # ---- QwtPlotItem API ------------------------------------------------------
     def draw_image(self, painter, canvasRect, srcRect, dstRect, xMap, yMap):
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
         x1, y1, x2, y2 = canvasRect.toAlignedRect().getCoords()
         i1, j1, i2, j2 = srcRect
 

plotpy/tests/widgets/test_dotarraydemo.py

@@ -102,6 +102,8 @@ def types(self) -> tuple[type[IItemType], ...]:
 
     def draw_image(self, painter, canvasRect, srcRect, dstRect, xMap, yMap):
         """Draw image"""
+        if self.warn_if_non_linear_scale(painter, canvasRect):
+            return
         painter.setRenderHint(QG.QPainter.Antialiasing, True)
         param = self.param
         xcoords = vmap(xMap, np.arange(0, param.dim_h + 1, param.step_x))