Rename flamegraph "Invert" button

We've adding a `--inverted` mode to `memray flamegraph` causing stacks
to be added to the flame graph in reverse order, so that the children of
the root are functions that performed allocations and the leaves are
thread entry points. Because of this change, we need a different name
for the "Invert" button that flips the entire flame graph upside down.

This commit introduces a new toggle button for switching between our
default "icicle graph" view (with the root at the top and allocations
dangling from it) and the traditional "flame graph" view (with the root
at the bottom and allocations rising up from it). The toggle button also
gives a visual indication of what mode you're in.

docs/flamegraph.rst

@@ -196,19 +196,24 @@ checkbox:
 Note that allocations in these frames will still be accounted for
 in parent frames, even if they're hidden.
 
-Inverted View
------------------
-
-Although the flame graphs explained above show the calling functions below
-and memory allocating functions above, flame graphs can be inverted
-so that the calling functions are at the top, while memory allocating
-functions are at the bottom. In this view, look for wide ceilings
-instead of wide plateaus to find functions with the largest allocation
-of memory.
-
-To invert the flame graph, press the *Invert* button:
+Flames versus Icicles
+---------------------
 
-.. image:: _static/images/invert_button.png
+The flame graphs explained above show each function above its caller,
+with the root at the bottom. This is what's traditionally called
+a "flame graph", because the wide base with narrowing columns above it
+looks sort of like a burning log with flames leaping into the air above
+it. Memray also supports what's sometimes called an "icicle graph",
+which has the root at the top. In an icicle graph, each function is
+below its caller, and there is a wide ceiling that thinner columns
+descend from, like icicles hanging from a roof. Whichever of these modes
+you choose, the data shown in the table is the same, just mirrored
+vertically.
+
+You can switch between showing a flame graph and an icicle graph with
+this toggle button:
+
+.. image:: _static/images/icicle_flame_toggle.png
     :align: center
 
 .. _memory-leaks-view:

src/memray/reporters/assets/flamegraph.js

@@ -77,7 +77,8 @@ function main() {
   }
 
   // Setup event handlers
-  document.getElementById("invertButton").onclick = onInvert;
+  document.getElementById("icicles").onchange = onInvert;
+  document.getElementById("flames").onchange = onInvert;
   document.getElementById("resetZoomButton").onclick = onResetZoom;
   document.getElementById("resetThreadFilterItem").onclick = onFilterThread;
   let hideUninterestingCheckBox = document.getElementById("hideUninteresting");

src/memray/reporters/assets/flamegraph_common.js

@@ -75,7 +75,7 @@ export function handleFragments() {
 
 // For the invert button
 export function onInvert() {
-  chart.inverted(!chart.inverted());
+  chart.inverted(this === document.getElementById("icicles"));
   chart.resetZoom(); // calls onClick
 }
 

src/memray/reporters/assets/temporal_flamegraph.js

@@ -323,7 +323,8 @@ function main() {
   }
 
   // Setup event handlers
-  document.getElementById("invertButton").onclick = onInvert;
+  document.getElementById("icicles").onchange = onInvert;
+  document.getElementById("flames").onchange = onInvert;
   document.getElementById("resetZoomButton").onclick = onResetZoom;
   document.getElementById("resetThreadFilterItem").onclick = onFilterThread;
   let hideUninterestingCheckBox = document.getElementById("hideUninteresting");

src/memray/reporters/templates/assets/flamegraph.css

@@ -88,3 +88,11 @@
   background-color: rgba(0, 0, 0, 0.5); /* semi-transparent black */
   z-index: 99; /* make sure it's on top of other elements */
 }
+
+.flamegraph-icon {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.flipped svg { transform: scale(1,-1); }

src/memray/reporters/templates/flamegraph.html

@@ -21,8 +21,29 @@
           title="Hide frames related to the Python import system" >
     <label class="form-check-label text-white bg-dark">Hide Import System Frames</label>
 </div>
+<div class="btn-group btn-group-toggle mr-3" data-toggle="buttons">
+  <label class="btn btn-outline-light shadow-none">
+    <input type="radio" name="flames/icicles" id="flames" autocomplete="off">
+    <div class="flamegraph-icon flipped">
+      <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" stroke-width="1" stroke="currentColor" fill="none" stroke-linecap="round" stroke-linejoin="round">
+        <path d="M 1 1 h 22 Z M 11 6 h 10 Z M 1 6 h 7 Z M 11 11 h 7 Z M 1 11 h 4 Z M 11 16 h 4 Z M 1 16 h 2 Z M 11 21 h 2 Z"/>
+      </svg>
+    </div>
+    &nbsp;
+    Flames
+  </label>
+  <label class="btn btn-outline-light active shadow-none">
+    <input type="radio" name="flames/icicles" id="icicles" autocomplete="off" checked/>
+    Icicles
+    &nbsp;
+    <div class="flamegraph-icon">
+      <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" stroke-width="1" stroke="currentColor" fill="none" stroke-linecap="round" stroke-linejoin="round">
+        <path d="M 1 1 h 22 Z M 11 6 h 10 Z M 1 6 h 7 Z M 11 11 h 7 Z M 1 11 h 4 Z M 11 16 h 4 Z M 1 16 h 2 Z M 11 21 h 2 Z"/>
+      </svg>
+    </div>
+  </label>
+</div>
 <button id="resetZoomButton" class="btn btn-outline-light mr-3">Reset Zoom</button>
-<button id="invertButton" class="btn btn-outline-light mr-3">Invert</button>
 {% endblock %}
 
 {% block content %}