[gtk/wip/ebassi/constraint-layout: 1/9] Fix the opposite size measurement in GtkConstraintLayout

[Emmanuele Bassi <ebassi src gnome org>]

commit e4466dd4fe12a2c14abd5f22466cb243261cac74
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Thu Jun 27 17:34:29 2019 +0100

    Fix the opposite size measurement in GtkConstraintLayout
    
    We cannot use the given "for size" when querying our children, because
    the constraint layout has no idea about the opposite size of its
    children until the layout is complete.
    
    Additionally, we should only suggest an opposite size for the layout if
    we have one, instead of suggesting a weak zero size.

 gtk/gtkconstraintlayout.c | 114 +++++++++++++++++++++-------------------------
 1 file changed, 52 insertions(+), 62 deletions(-)
---
diff --git a/gtk/gtkconstraintlayout.c b/gtk/gtkconstraintlayout.c
index a111dbe591..86cdd2840f 100644
--- a/gtk/gtkconstraintlayout.c
+++ b/gtk/gtkconstraintlayout.c
@@ -693,57 +693,47 @@ gtk_constraint_layout_measure (GtkLayoutManager *manager,
 
       child_info = GTK_CONSTRAINT_LAYOUT_CHILD (gtk_layout_manager_get_layout_child (manager, child));
 
-      gtk_widget_measure (child, orientation, for_size,
+      gtk_widget_measure (child, orientation, -1,
                           &min_size, &nat_size,
                           NULL, NULL);
 
-      switch (orientation)
-        {
-        case GTK_ORIENTATION_HORIZONTAL:
-          width_var = get_child_attribute (child_info, solver, child,
-                                           GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
-
-          constraint =
-            gtk_constraint_solver_add_constraint (solver,
-                                                  width_var,
-                                                  GTK_CONSTRAINT_RELATION_GE,
-                                                  gtk_constraint_expression_new (min_size),
-                                                  GTK_CONSTRAINT_WEIGHT_REQUIRED);
-          g_ptr_array_add (size_constraints, constraint);
-
-          constraint =
-            gtk_constraint_solver_add_constraint (solver,
-                                                  width_var,
-                                                  GTK_CONSTRAINT_RELATION_EQ,
-                                                  gtk_constraint_expression_new (nat_size),
-                                                  GTK_CONSTRAINT_WEIGHT_MEDIUM);
-          g_ptr_array_add (size_constraints, constraint);
-          break;
-
-        case GTK_ORIENTATION_VERTICAL:
-          height_var = get_child_attribute (child_info, solver, child,
-                                            GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
-
-          constraint =
-            gtk_constraint_solver_add_constraint (solver,
-                                                  height_var,
-                                                  GTK_CONSTRAINT_RELATION_GE,
-                                                  gtk_constraint_expression_new (min_size),
-                                                  GTK_CONSTRAINT_WEIGHT_REQUIRED);
-          g_ptr_array_add (size_constraints, constraint);
-
-          constraint =
-            gtk_constraint_solver_add_constraint (solver,
-                                                  height_var,
-                                                  GTK_CONSTRAINT_RELATION_EQ,
-                                                  gtk_constraint_expression_new (nat_size),
-                                                  GTK_CONSTRAINT_WEIGHT_MEDIUM);
-          g_ptr_array_add (size_constraints, constraint);
-          break;
-
-        default:
-          break;
-        }
+      width_var = get_child_attribute (child_info, solver, child,
+                                       GTK_CONSTRAINT_ATTRIBUTE_WIDTH);
+
+      constraint =
+        gtk_constraint_solver_add_constraint (solver,
+                                              width_var,
+                                              GTK_CONSTRAINT_RELATION_GE,
+                                              gtk_constraint_expression_new (min_size),
+                                              GTK_CONSTRAINT_WEIGHT_REQUIRED);
+      g_ptr_array_add (size_constraints, constraint);
+
+      constraint =
+        gtk_constraint_solver_add_constraint (solver,
+                                              width_var,
+                                              GTK_CONSTRAINT_RELATION_EQ,
+                                              gtk_constraint_expression_new (nat_size),
+                                              GTK_CONSTRAINT_WEIGHT_MEDIUM);
+      g_ptr_array_add (size_constraints, constraint);
+
+      height_var = get_child_attribute (child_info, solver, child,
+                                        GTK_CONSTRAINT_ATTRIBUTE_HEIGHT);
+
+      constraint =
+        gtk_constraint_solver_add_constraint (solver,
+                                              height_var,
+                                              GTK_CONSTRAINT_RELATION_GE,
+                                              gtk_constraint_expression_new (min_size),
+                                              GTK_CONSTRAINT_WEIGHT_REQUIRED);
+      g_ptr_array_add (size_constraints, constraint);
+
+      constraint =
+        gtk_constraint_solver_add_constraint (solver,
+                                              height_var,
+                                              GTK_CONSTRAINT_RELATION_EQ,
+                                              gtk_constraint_expression_new (nat_size),
+                                              GTK_CONSTRAINT_WEIGHT_MEDIUM);
+      g_ptr_array_add (size_constraints, constraint);
     }
 
   switch (orientation)
@@ -769,15 +759,22 @@ gtk_constraint_layout_measure (GtkLayoutManager *manager,
    * natural state of the system. Once we get the value out, we can
    * remove these constraints
    */
-  gtk_constraint_solver_add_edit_variable (solver, size, GTK_CONSTRAINT_WEIGHT_WEAK + 1);
-  gtk_constraint_solver_add_edit_variable (solver, opposite_size, GTK_CONSTRAINT_WEIGHT_WEAK + 2);
-
-  gtk_constraint_solver_begin_edit (solver);
+  if (for_size > 0)
+    {
+      gtk_constraint_solver_add_edit_variable (solver, opposite_size, GTK_CONSTRAINT_WEIGHT_MEDIUM * 2.0);
+      gtk_constraint_solver_begin_edit (solver);
+      gtk_constraint_solver_suggest_value (solver, opposite_size, for_size);
+      gtk_constraint_solver_resolve (solver);
 
-  gtk_constraint_solver_suggest_value (solver, size, 0.0);
-  gtk_constraint_solver_suggest_value (solver, opposite_size, for_size >= 0 ? for_size : 0.0);
+      value = gtk_constraint_variable_get_value (size);
 
-  gtk_constraint_solver_resolve (solver);
+      gtk_constraint_solver_remove_edit_variable (solver, opposite_size);
+      gtk_constraint_solver_end_edit (solver);
+    }
+  else
+    {
+      value = gtk_constraint_variable_get_value (size);
+    }
 
   GTK_NOTE (LAYOUT,
             g_print ("layout %p preferred %s size: %.3f (for opposite size: %d)\n",
@@ -786,13 +783,6 @@ gtk_constraint_layout_measure (GtkLayoutManager *manager,
                      gtk_constraint_variable_get_value (size),
                      for_size));
 
-  value = gtk_constraint_variable_get_value (size);
-
-  gtk_constraint_solver_remove_edit_variable (solver, size);
-  gtk_constraint_solver_remove_edit_variable (solver, opposite_size);
-
-  gtk_constraint_solver_end_edit (solver);
-
   for (guint i = 0; i < size_constraints->len; i++)
     {
       GtkConstraintRef *ref = g_ptr_array_index (size_constraints, i);