HeatMap: Allow setting the center when using diverging palettes

Orange/widgets/utils/colorgradientselection.py

@@ -2,26 +2,29 @@
 
 from AnyQt.QtCore import Qt, QSize, QAbstractItemModel, Property
 from AnyQt.QtWidgets import (
-    QWidget, QSlider, QFormLayout, QComboBox, QStyle
-)
+    QWidget, QSlider, QFormLayout, QComboBox, QStyle,
+    QHBoxLayout, QLineEdit, QLabel)
 from AnyQt.QtCore import Signal
+from AnyQt.QtGui import QFontMetrics, QDoubleValidator
 
-from Orange.widgets.utils import itemmodels
+from Orange.widgets.utils import itemmodels, colorpalettes
 
 
 class ColorGradientSelection(QWidget):
     activated = Signal(int)
 
     currentIndexChanged = Signal(int)
     thresholdsChanged = Signal(float, float)
+    centerChanged = Signal(float)
 
-    def __init__(self, *args, thresholds=(0.0, 1.0), **kwargs):
+    def __init__(self, *args, thresholds=(0.0, 1.0), center=0, **kwargs):
         super().__init__(*args, **kwargs)
 
         low = round(clip(thresholds[0], 0., 1.), 2)
         high = round(clip(thresholds[1], 0., 1.), 2)
         high = max(low, high)
         self.__threshold_low, self.__threshold_high = low, high
+        self.__center = center
         form = QFormLayout(
             formAlignment=Qt.AlignLeft,
             labelAlignment=Qt.AlignLeft,
@@ -42,6 +45,21 @@ def __init__(self, *args, thresholds=(0.0, 1.0), **kwargs):
         self.gradient_cb.setModel(model)
         self.gradient_cb.activated[int].connect(self.activated)
         self.gradient_cb.currentIndexChanged.connect(self.currentIndexChanged)
+        self.gradient_cb.currentIndexChanged.connect(self.__on_palette_changed)
+
+        self.center_box = QWidget()
+        center_layout = QHBoxLayout()
+        self.center_box.setLayout(center_layout)
+        width = QFontMetrics(self.font()).boundingRect("9999999").width()
+        self.center_edit = QLineEdit(
+            text=f"{self.__center}",
+            maximumWidth=width, placeholderText="0", alignment=Qt.AlignRight)
+        self.center_edit.setValidator(QDoubleValidator())
+        self.center_edit.editingFinished.connect(self.__on_center_changed)
+        center_layout.setContentsMargins(0, 0, 0, 0)
+        center_layout.addStretch(1)
+        center_layout.addWidget(QLabel("Centered at"))
+        center_layout.addWidget(self.center_edit)
 
         slider_low = QSlider(
             objectName="threshold-low-slider", minimum=0, maximum=100,
@@ -60,6 +78,7 @@ def __init__(self, *args, thresholds=(0.0, 1.0), **kwargs):
                               "gradient from the higher end")
         )
         form.setWidget(0, QFormLayout.SpanningRole, self.gradient_cb)
+        form.setWidget(1, QFormLayout.FieldRole, self.center_box)
         form.addRow(self.tr("Low:"), slider_low)
         form.addRow(self.tr("High:"), slider_high)
         self.slider_low = slider_low
@@ -109,6 +128,14 @@ def thresholdHigh(self) -> float:
     def setThresholdHigh(self, high: float) -> None:
         self.setThresholds(min(self.__threshold_low, high), high)
 
+    def center(self) -> float:
+        return self.__center
+
+    def setCenter(self, center: float) -> None:
+        self.__center = center
+        self.center_edit.setText(f"{center}")
+        self.centerChanged.emit(center)
+
     thresholdHigh_ = Property(
         float, thresholdLow, setThresholdLow, notify=thresholdsChanged)
 
@@ -146,6 +173,15 @@ def setThresholds(self, low: float, high: float) -> None:
             self.slider_high.setSliderPosition(high * 100)
             self.thresholdsChanged.emit(high, low)
 
+    def __on_palette_changed(self):
+        palette = self.currentData()
+        self.center_box.setVisible(
+            isinstance(palette, colorpalettes.Palette)
+            and palette.flags & palette.Flags.Diverging)
+
+    def __on_center_changed(self):
+        self.__center = float(self.center_edit.text() or "0")
+        self.centerChanged.emit(self.__center)
 
 def clip(a, amin, amax):
     return min(max(a, amin), amax)

Orange/widgets/visualize/owheatmap.py

@@ -155,6 +155,7 @@ class Outputs:
 
     threshold_low = settings.Setting(0.0)
     threshold_high = settings.Setting(1.0)
+    color_center = settings.Setting(0)
 
     merge_kmeans = settings.Setting(False)
     merge_kmeans_k = settings.Setting(50)
@@ -244,6 +245,7 @@ def _():
 
         self.color_map_widget = cmw = ColorGradientSelection(
             thresholds=(self.threshold_low, self.threshold_high),
+            center=self.color_center
         )
         model = itemmodels.ContinuousPalettesModel(parent=self)
         cmw.setModel(model)
@@ -257,6 +259,12 @@ def _set_thresholds(low, high):
             self.threshold_low, self.threshold_high = low, high
             self.update_color_schema()
         cmw.thresholdsChanged.connect(_set_thresholds)
+
+        def _set_centering(center):
+            self.color_center = center
+            self.update_color_schema()
+        cmw.centerChanged.connect(_set_centering)
+
         colorbox.layout().addWidget(self.color_map_widget)
 
         mergebox = gui.vBox(self.controlArea, "Merge",)
@@ -449,7 +457,7 @@ def color_palette(self):
     def color_map(self) -> GradientColorMap:
         return GradientColorMap(
             self.color_palette(), (self.threshold_low, self.threshold_high),
-            0 if self.center_palette else None
+            self.color_map_widget.center() if self.center_palette else None
         )
 
     def clear(self):