From 8c781f59c587ed3a162ac36f8dddf5df9b01db51 Mon Sep 17 00:00:00 2001
From: Sergey Yaroslavtsev <sergey.yaroslavtsev@esrf.fr>
Date: Thu, 23 Jul 2026 23:22:14 +0200
Subject: [PATCH] partially fix the grid isue for mosaic mask

---
 src/PyMca5/PyMcaGui/pymca/QStackWidget.py | 35 +++++++++++++++++++----
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/src/PyMca5/PyMcaGui/pymca/QStackWidget.py b/src/PyMca5/PyMcaGui/pymca/QStackWidget.py
index d24e9f1a1..b929831dd 100644
--- a/src/PyMca5/PyMcaGui/pymca/QStackWidget.py
+++ b/src/PyMca5/PyMcaGui/pymca/QStackWidget.py
@@ -1325,8 +1325,10 @@ def _configureScatterMode(self, scatter):
                     self._scatterStackView = MaskScatterViewWidget(parent=self.stackWindow, backend="mpl")
                 except:
                     self._scatterStackView = MaskScatterViewWidget(parent=self.stackWindow, backend="gl")
-                irregular = silx_items.Scatter.Visualization.IRREGULAR_GRID
-                self._scatterStackView.setVisualizationMode(irregular)
+                # Always start by displaying the data at the true motor positions
+                # without requiring a guessable grid.
+                solid = silx_items.Scatter.Visualization.SOLID
+                self._scatterStackView.setVisualizationMode(solid)
                 self._scatterStackView.setSelectionReadOnly()
                 # insert the scatter view in the origin
                 sidx = self.stackWindow.mainLayout.indexOf(self.stackWidget)
@@ -1336,7 +1338,7 @@ def _configureScatterMode(self, scatter):
                     self._scatterRoiView = MaskScatterViewWidget(parent=self.roiWindow, backend="mpl")
                 except:
                     self._scatterRoiView = MaskScatterViewWidget(parent=self.roiWindow, backend="gl")
-                self._scatterRoiView.setVisualizationMode(irregular)
+                self._scatterRoiView.setVisualizationMode(solid)
                 # show mask tool on start
                 self._scatterRoiView.setMaskToolsVisible(True)
                 # insert the scatter view in the roi
@@ -1415,12 +1417,35 @@ def _setRoiWidgetGridImage(self):
 
     def _scatterRegularGridImage(self):
         item = self._scatterRoiView.getScatterView().getScatterItem()
-        guess = _guess_grid(item.getXData(copy=False), item.getYData(copy=False))
+        x = item.getXData(copy=False)
+        y = item.getYData(copy=False)
+        values = numpy.asarray(item.getValueData(copy=False), dtype=numpy.float64)
+        # Try as is
+        image = self._reshapeOnGuessedGrid(x, y, values)
+        if image is not None:
+            return image
+        # Try if it is a mosaic map.
+        # Try both axes as primary.
+        for keys in ((y, x), (x, y)):
+            order = numpy.lexsort(keys)
+            image = self._reshapeOnGuessedGrid(x[order], y[order],
+                                               values[order], require2D=True)
+            if image is not None:
+                return image
+        return None
+
+    def _reshapeOnGuessedGrid(self, x, y, values, require2D=False):
+        """
+        Reshape ``values`` onto the regular grid by silx guess.
+        ``require2D`` reject 1xN grid.
+        """
+        guess = _guess_grid(x, y)
         if guess is None:
             return None
         order, (height, width) = guess
+        if require2D and (height < 2 or width < 2):
+            return None
         # nan padding (before padding was done only for the visualisation)
-        values = numpy.asarray(item.getValueData(copy=False), dtype=numpy.float64)
         image = numpy.full(height * width, numpy.nan, dtype=numpy.float64)
         image[:values.size] = values
         if order == "row":