From cd06a025a4f19400f7935979b4da502cf6c9c6ff Mon Sep 17 00:00:00 2001
From: Christian Hergert <chergert@redhat.com>
Date: Fri, 25 Aug 2023 15:16:45 -0700
Subject: [PATCH] sysprof: render from alternate root to real root

This helps with the situation where we are going to render the parents
of the selected root first, and want them to take the whole width. Next
step is to support invalidation of the rendering.
---
 src/sysprof/sysprof-flame-graph.c | 77 ++++++++++++++++++++++++++-----
 1 file changed, 66 insertions(+), 11 deletions(-)

diff --git a/src/sysprof/sysprof-flame-graph.c b/src/sysprof/sysprof-flame-graph.c
index 9d0290cc..85113de6 100644
--- a/src/sysprof/sysprof-flame-graph.c
+++ b/src/sysprof/sysprof-flame-graph.c
@@ -529,7 +529,8 @@ sysprof_flame_graph_generate_cb (GObject      *object,
 static void
 generate (GArray                *array,
           SysprofCallgraphNode  *node,
-          const graphene_rect_t *area)
+          const graphene_rect_t *area,
+          gboolean               recurse)
 {
   FlameRectangle rect;
 
@@ -545,7 +546,7 @@ generate (GArray                *array,
 
   g_array_append_val (array, rect);
 
-  if (node->children != NULL)
+  if (recurse && node->children != NULL)
     {
       graphene_rect_t child_area;
 
@@ -562,7 +563,7 @@ generate (GArray                *array,
 
           child_area.size.width = width;
 
-          generate (array, child, &child_area);
+          generate (array, child, &child_area, TRUE);
 
           child_area.origin.x += width;
         }
@@ -591,24 +592,73 @@ sort_by_coord (gconstpointer a,
   return 0;
 }
 
+typedef struct
+{
+  SysprofCallgraph     *callgraph;
+  SysprofCallgraphNode *root;
+} Generate;
+
+static void
+generate_free (Generate *g)
+{
+  g_object_unref (g->callgraph);
+  g->root = NULL;
+  g_free (g);
+}
+
 static void
 sysprof_flame_graph_generate_worker (GTask        *task,
                                      gpointer      source_object,
                                      gpointer      task_data,
                                      GCancellable *cancellable)
 {
-  SysprofCallgraph *callgraph = task_data;
+  Generate *g = task_data;
+  SysprofCallgraphNode **ancestors;
   g_autoptr(GArray) array = NULL;
+  graphene_rect_t area;
+  guint size;
   int height;
 
-  g_assert (SYSPROF_IS_CALLGRAPH (callgraph));
+  g_assert (g!= NULL);
+  g_assert (SYSPROF_IS_CALLGRAPH (g->callgraph));
+  g_assert (g->root != NULL);
 
-  array = g_array_sized_new (FALSE, FALSE, sizeof (FlameRectangle), callgraph->root.count);
-  height = callgraph->height * ROW_HEIGHT + callgraph->height + 1;
+  size = g->root->count + g->callgraph->height;
+  array = g_array_sized_new (FALSE, FALSE, sizeof (FlameRectangle), size);
+  height = g->callgraph->height * ROW_HEIGHT + g->callgraph->height + 1;
+  area = GRAPHENE_RECT_INIT (0, 0, G_MAXUINT16, height);
 
-  generate (array,
-            &callgraph->root,
-            &GRAPHENE_RECT_INIT (0, 0, G_MAXUINT16, height));
+  if (g->root->parent != NULL)
+    {
+      guint n_ancestors = 0;
+      int i;
+
+      /* Synthesize parents so we can draw recursively but have the
+       * important data copied from the parents.
+       */
+
+      for (SysprofCallgraphNode *iter = g->root->parent; iter; iter = iter->parent)
+        n_ancestors++;
+
+      ancestors = g_alloca0 (sizeof (SysprofCallgraphNode *) * n_ancestors);
+
+      g_assert (n_ancestors > 0);
+      g_assert (ancestors != NULL);
+
+      i = n_ancestors-1;
+      for (SysprofCallgraphNode *iter = g->root->parent; iter; iter = iter->parent, i--)
+        ancestors[i] = iter;
+
+      for (i = 0; i < n_ancestors; i++)
+        {
+          generate (array, ancestors[i], &area, FALSE);
+
+          area.size.height -= ROW_HEIGHT;
+          area.size.height -= 1;
+        }
+    }
+
+  generate (array, g->root, &area, TRUE);
 
   g_array_sort (array, sort_by_coord);
 
@@ -635,11 +685,16 @@ sysprof_flame_graph_set_callgraph (SysprofFlameGraph *self,
       if (callgraph != NULL)
         {
           g_autoptr(GTask) task = NULL;
+          Generate *g;
 
           self->root = &callgraph->root;
 
+          g = g_new0 (Generate, 1);
+          g->callgraph = g_object_ref (callgraph);
+          g->root = self->root;
+
           task = g_task_new (NULL, NULL, sysprof_flame_graph_generate_cb, g_object_ref (self));
-          g_task_set_task_data (task, g_object_ref (callgraph), g_object_unref);
+          g_task_set_task_data (task, g, (GDestroyNotify)generate_free);
           g_task_run_in_thread (task, sysprof_flame_graph_generate_worker);
         }