paned: Compute the right handle size

Testcase included

Fixes #4469

gtk/gtkpaned.c

@@ -1160,7 +1160,7 @@ gtk_paned_get_preferred_size_for_opposite_orientation (GtkWidget      *widget,
                                                        int            *natural)
 {
   GtkPaned *paned = GTK_PANED (widget);
-  int for_start_child, for_end_child;
+  int for_start_child, for_end_child, for_handle;
   int child_min, child_nat;
 
   if (size > -1 &&
@@ -1168,22 +1168,21 @@ gtk_paned_get_preferred_size_for_opposite_orientation (GtkWidget      *widget,
       paned->end_child && gtk_widget_get_visible (paned->end_child))
     {
       int start_child_req, end_child_req;
-      int handle_size;
 
       gtk_widget_measure (paned->handle_widget,
-                          OPPOSITE_ORIENTATION (paned->orientation),
+                          paned->orientation,
                           -1,
-                          NULL, &handle_size,
+                          NULL, &for_handle,
                           NULL, NULL);
 
       gtk_widget_measure (paned->start_child, paned->orientation, -1, &start_child_req, NULL, NULL, NULL);
       gtk_widget_measure (paned->end_child, paned->orientation, -1, &end_child_req, NULL, NULL, NULL);
 
       gtk_paned_compute_position (paned,
-                                  size - handle_size, start_child_req, end_child_req,
+                                  size - for_handle, start_child_req, end_child_req,
                                   NULL, NULL, &for_start_child);
 
-      for_end_child = size - for_start_child - handle_size;
+      for_end_child = size - for_start_child - for_handle;
 
       if (paned->shrink_start_child)
         for_start_child = MAX (start_child_req, for_start_child);
@@ -1194,6 +1193,7 @@ gtk_paned_get_preferred_size_for_opposite_orientation (GtkWidget      *widget,
     {
       for_start_child = size;
       for_end_child = size;
+      for_handle = -1;
     }
 
   *minimum = *natural = 0;
@@ -1202,7 +1202,7 @@ gtk_paned_get_preferred_size_for_opposite_orientation (GtkWidget      *widget,
     {
       gtk_widget_measure (paned->start_child,
                           OPPOSITE_ORIENTATION (paned->orientation),
-                          MAX (for_start_child, -1),
+                          for_start_child,
                           &child_min, &child_nat,
                           NULL, NULL);
 
@@ -1214,7 +1214,20 @@ gtk_paned_get_preferred_size_for_opposite_orientation (GtkWidget      *widget,
     {
       gtk_widget_measure (paned->end_child,
                           OPPOSITE_ORIENTATION (paned->orientation),
-                          MAX (for_end_child, -1),
+                          for_end_child,
+                          &child_min, &child_nat,
+                          NULL, NULL);
+
+      *minimum = MAX (*minimum, child_min);
+      *natural = MAX (*natural, child_nat);
+    }
+
+  if (paned->start_child && gtk_widget_get_visible (paned->start_child) &&
+      paned->end_child && gtk_widget_get_visible (paned->end_child))
+    {
+      gtk_widget_measure (paned->handle_widget,
+                          OPPOSITE_ORIENTATION (paned->orientation),
+                          for_handle,
                           &child_min, &child_nat,
                           NULL, NULL);
 

testsuite/reftests/meson.build

@@ -427,6 +427,9 @@ testdata = [
   'opacity-initial.ui',
   'overlay-no-main-widget.ref.ui',
   'overlay-no-main-widget.ui',
+  'paned-handle-size.css',
+  'paned-handle-size.ref.ui',
+  'paned-handle-size.ui',
   'paned-undersized.css',
   'paned-undersized.ref.ui',
   'paned-undersized.ui',

testsuite/reftests/paned-handle-size.css

@@ -0,0 +1,15 @@
+paned separator,
+picture {
+  all: unset;
+  background: firebrick;
+}
+
+paned.vertical > separator {
+  min-width: 10px;
+  min-height: 20px;
+}
+
+paned.horizontal > separator {
+  min-width: 20px;
+  min-height: 10px;
+}

testsuite/reftests/paned-handle-size.ref.ui

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface domain="gtk40">
+  <object class="GtkWindow">
+    <property name="decorated">0</property>
+    <child>
+      <object class="GtkBox">
+        <child>
+          <object class="GtkBox">
+            <property name="orientation">vertical</property>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">top left</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkPicture">
+                <property name="height-request">20</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">bottom left</property>
+              </object>
+            </child>
+          </object>
+        </child>
+        <child>
+          <object class="GtkPicture">
+            <property name="width-request">20</property>
+          </object>
+        </child>
+        <child>
+          <object class="GtkBox">
+            <property name="orientation">vertical</property>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">top right</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkPicture">
+                <property name="height-request">20</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">bottom right</property>
+              </object>
+            </child>
+          </object>
+        </child>
+      </object>
+    </child>
+  </object>
+</interface>

testsuite/reftests/paned-handle-size.ui

@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<interface domain="gtk40">
+  <object class="GtkWindow">
+    <property name="decorated">0</property>
+    <child>
+      <object class="GtkPaned">
+        <child>
+          <object class="GtkPaned">
+            <property name="orientation">vertical</property>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">top left</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">bottom left</property>
+              </object>
+            </child>
+          </object>
+        </child>
+        <child>
+          <object class="GtkPaned">
+            <property name="orientation">vertical</property>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">top right</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkLabel">
+                <property name="label">bottom right</property>
+              </object>
+            </child>
+          </object>
+        </child>
+      </object>
+    </child>
+  </object>
+</interface>