From f9f98593e04a815edfe1f80c16f6b54890950bda Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Thu, 29 Jun 2017 11:37:08 +1000
Subject: [PATCH] Draw links between dependent parameters in graphical modeler

Fix #12907
---
 .../processing/modeler/ModelerArrowItem.py      | 14 +++++++++++++-
 .../processing/modeler/ModelerGraphicItem.py    |  5 ++++-
 .../plugins/processing/modeler/ModelerScene.py  | 17 +++++++++++++++++
 3 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/python/plugins/processing/modeler/ModelerArrowItem.py b/python/plugins/processing/modeler/ModelerArrowItem.py
index 7c079defece..5392d240653 100644
--- a/python/plugins/processing/modeler/ModelerArrowItem.py
+++ b/python/plugins/processing/modeler/ModelerArrowItem.py
@@ -70,11 +70,23 @@ class ModelerArrowItem(QGraphicsPathItem):
                          Qt.RoundCap, Qt.RoundJoin))
         self.setZValue(0)
 
+    def setPenStyle(self, style):
+        pen = self.pen()
+        pen.setStyle(style)
+        self.setPen(pen)
+        self.update()
+
     def updatePath(self):
         self.endPoints = []
         controlPoints = []
         endPt = self.endItem.getLinkPointForParameter(self.endIndex)
-        startPt = self.startItem.getLinkPointForOutput(self.startIndex)
+        if isinstance(self.startItem.element, QgsProcessingModelAlgorithm.ModelParameter):
+            startPt = self.startItem.getLinkPointForParameter(self.startIndex)
+        else:
+            startPt = self.startItem.getLinkPointForOutput(self.startIndex)
+        if isinstance(self.endItem.element, QgsProcessingModelAlgorithm.ModelParameter):
+            endPt = self.endItem.getLinkPointForParameter(self.startIndex)
+
         if isinstance(self.startItem.element, QgsProcessingModelAlgorithm.ChildAlgorithm):
             if self.startIndex != -1:
                 controlPoints.append(self.startItem.pos() + startPt)
diff --git a/python/plugins/processing/modeler/ModelerGraphicItem.py b/python/plugins/processing/modeler/ModelerGraphicItem.py
index 149e74d6c19..33bd83ee1a2 100644
--- a/python/plugins/processing/modeler/ModelerGraphicItem.py
+++ b/python/plugins/processing/modeler/ModelerGraphicItem.py
@@ -199,7 +199,7 @@ class ModelerGraphicItem(QGraphicsItem):
                 self.element.setDescription(dlg.param.name())
                 self.model.addModelParameter(dlg.param, self.element)
                 self.text = dlg.param.description()
-                self.update()
+                self.scene.dialog.repaintModel()
         elif isinstance(self.element, QgsProcessingModelAlgorithm.ChildAlgorithm):
             dlg = None
             try:
@@ -336,6 +336,9 @@ class ModelerGraphicItem(QGraphicsItem):
         if isinstance(self.element, QgsProcessingModelAlgorithm.ChildAlgorithm) and self.element.parametersCollapsed():
             paramIndex = -1
             offsetX = 17
+        if isinstance(self.element, QgsProcessingModelAlgorithm.ModelParameter):
+            paramIndex = -1
+            offsetX = 0
         font = QFont('Verdana', 8)
         font.setPixelSize(12)
         fm = QFontMetricsF(font)
diff --git a/python/plugins/processing/modeler/ModelerScene.py b/python/plugins/processing/modeler/ModelerScene.py
index 542fcbc5a68..b1bcd659ee3 100644
--- a/python/plugins/processing/modeler/ModelerScene.py
+++ b/python/plugins/processing/modeler/ModelerScene.py
@@ -94,6 +94,22 @@ class ModelerScene(QGraphicsScene):
             item.setPos(inp.position().x(), inp.position().y())
             self.paramItems[inp.parameterName()] = item
 
+        # Input dependency arrows
+        for input_name in list(model.parameterComponents().keys()):
+            idx = 0
+            parameter_def = model.parameterDefinition(input_name)
+            if hasattr(parameter_def, 'parentLayerParameter') and parameter_def.parentLayerParameter():
+                parent_name = parameter_def.parentLayerParameter()
+                if input_name in self.paramItems and parent_name in self.paramItems:
+                    input_item = self.paramItems[input_name]
+                    parent_item = self.paramItems[parent_name]
+                    arrow = ModelerArrowItem(parent_item, -1, input_item, -1)
+                    input_item.addArrow(arrow)
+                    parent_item.addArrow(arrow)
+                    arrow.setPenStyle(Qt.DotLine)
+                    arrow.updatePath()
+                    self.addItem(arrow)
+
         # We add the algs
         for alg in list(model.childAlgorithms().values()):
             item = ModelerGraphicItem(alg, model, controls, scene=self)
@@ -104,6 +120,7 @@ class ModelerScene(QGraphicsScene):
             self.algItems[alg.childId()] = item
 
         # And then the arrows
+
         for alg in list(model.childAlgorithms().values()):
             idx = 0
             for parameter in alg.algorithm().parameterDefinitions():