flamegraph widget: implement scroll

flameshow/models.py

@@ -108,6 +108,8 @@ class Profile:
     # init by post_init
     lines: List = field(init=False)
 
+    frameid_to_lineno: Dict[int, int] = field(init=False)
+
     def __post_init__(self):
         """
         init_lines must be called before render
@@ -120,6 +122,7 @@ def __post_init__(self):
         lines = [
             [root],
         ]
+        frameid_to_lineno = {0: 0}
         current = root.children
         line_no = 1
 
@@ -129,6 +132,7 @@ def __post_init__(self):
 
             for child in current:
                 line.append(child)
+                frameid_to_lineno[child._id] = line_no
                 next_line.extend(child.children)
 
             lines.append(line)
@@ -138,3 +142,4 @@ def __post_init__(self):
         t2 = time.time()
         logger.info("create lines done, took %.2f seconds", t2 - t1)
         self.lines = lines
+        self.frameid_to_lineno = frameid_to_lineno

flameshow/render/app.py

@@ -25,9 +25,13 @@
 
 class FlameGraphScroll(VerticalScroll, inherit_bindings=False):
     BINDINGS: ClassVar[list[BindingType]] = [
-        Binding("b", "scroll_up", "Scroll Up", show=True, key_display="B"),
+        Binding("b", "page_up", "Scroll Page Up", show=True, key_display="B"),
         Binding(
-            "f,space", "scroll_down", "Scroll Down", show=True, key_display="F"
+            "f,space",
+            "page_down",
+            "Scroll Page Down",
+            show=True,
+            key_display="F",
         ),
         Binding("home", "scroll_home", "Scroll Home", show=False),
         Binding("end", "scroll_end", "Scroll End", show=False),
@@ -199,8 +203,14 @@ async def handle_view_frame_changed(self, e):
         new_frame = e.frame
         self.view_frame = new_frame
 
-        flamegraph = self.query_one("FlameGraph")
-        flamegraph.view_frame = new_frame
+        with self.batch_update():
+            flamegraph = self.query_one("FlameGraph")
+            flamegraph.view_frame = new_frame
+
+            region = flamegraph.get_scroll_region(new_frame)
+            if region:
+                container = self.query_one("#flamegraph-out-container")
+                container.scroll_to_region(region)
 
     async def watch_sample_index(self, sample_index):
         logger.info("sample index changed to %d", sample_index)

flameshow/render/flamegraph.py

@@ -2,14 +2,15 @@
 from functools import lru_cache
 import logging
 import time
-from typing import Dict, List
+from typing import Dict, List, Union
 
 import iteround
 from rich.segment import Segment
 from rich.style import Style
 from textual.binding import Binding
 from textual.color import Color
 from textual.events import Resize
+from textual.geometry import Region
 from textual.message import Message
 from textual.reactive import reactive
 from textual.strip import Strip
@@ -70,15 +71,17 @@ def __init__(
         # pre-render
         self.frame_maps = None
 
+        # manually maintain the offset
+        self.current_crop = None
+
     def render_lines(self, crop):
-        logger.info("render_lines!! crop: %s", crop)
         my_width = crop.size.width
-        t1 = time.time()
         self.frame_maps = self.generate_frame_maps(
             my_width, self.focused_stack_id
         )
-        t2 = time.time()
-        logger.info("Generates frame maps, took %.4f seconds", t2 - t1)
+
+        self.current_crop = crop
+
         return super().render_lines(crop)
 
     @lru_cache
@@ -88,6 +91,7 @@ def generate_frame_maps(self, width, focused_stack_id):
 
         only re-computes with width, focused_stack changing
         """
+        t1 = time.time()
         logger.info(
             "lru cache miss, Generates frame map, for width=%d,"
             " focused_stack_id=%s",
@@ -163,7 +167,8 @@ def _generate_for_children(frame):
                 _generate_for_children(child)
 
         _generate_for_children(current_focused_stack)
-
+        t2 = time.time()
+        logger.info("Generates frame maps done, took %.4f seconds", t2 - t1)
         return frame_maps
 
     def render_line(self, y: int) -> Strip:
@@ -279,6 +284,17 @@ def action_move_down(self):
             return
         self.post_message(self.ViewFrameChanged(new_view_info_frame))
 
+    def get_scroll_region(self, frame) -> Union[None, Region]:
+        crop = self.current_crop
+        frame_line_no = self.profile.frameid_to_lineno[frame._id]
+        start_y = max(0, frame_line_no - round(crop.height / 2))
+        if start_y == crop.y == 0:
+            return None
+        display_region = Region(crop.x, start_y, crop.width, crop.height)
+        logger.info("scroll to %s", display_region)
+        # self.scroll_to_region(display_region, top=True)
+        return display_region
+
     def _get_biggest_exist_child(self, stacks):
         biggest = max(stacks, key=lambda s: s.values[self.sample_index])
         return biggest