fix(web): resolve rendering bug of sub-second timeline revisions (#558)

* fix(web): resolve rendering bug of sub-second timeline revisions

The timeline visualizer previously failed to render revisions with durations shorter than 1 second properly.

This was caused by an integer underflow in the vertex shader (`revision-v2.vertex.glsl`) when calculating the lower bound for clipping (`minTime.y`). By subtracting `1e10-1.0` (which is too large to safely cast to a uint) from `vs.leftEdgeTime.y`, the calculation yielded a corrupted huge number. The subsequent component-wise `max(time.xy, minTime)` overwrote the starting nanoseconds (`time.y`) with this corrupt number, resulting in incorrect width calculations for sub-second revisions.
The shader logic has been updated to set the nanosecond bound `minTime.y` explicitly to `0`. This securely preserves the actual nanoseconds `time.y` when applying the component-wise max.
Also added a new `DenseRevisions` story in `timeline-chart.stories.ts` to test high-density short revisions.

Fixe #557

* Fix issues pointed by gemini code assist

Author: kyasbal

web/src/app/timeline/components/timeline-chart.stories.ts

@@ -261,3 +261,43 @@ export const Composer: Story = {
     activeLogsIndices: composerBuilder.getAllActiveLogIndices(),
   },
 };
+
+function generateMockDenseRevisionsViewModel(): DemoViewModelBuilder {
+  const testDuration = 200 * 10; // 2 seconds (10 revisions * 200ms)
+  const builder = new DemoViewModelBuilder(
+    START_TIME,
+    START_TIME + testDuration,
+  );
+
+  const revisions = [];
+  for (let i = 0; i < 10; i++) {
+    revisions.push(
+      builder.createRevision(
+        START_TIME + i * 200,
+        START_TIME + (i + 1) * 200,
+        i % 2 === 0
+          ? RevisionState.RevisionStateExisting
+          : RevisionState.RevisionStateInferred,
+        RevisionVerb.RevisionVerbUpdate,
+      ),
+    );
+  }
+
+  builder.createTimeline(
+    'core/v1#pod#default#dense-revisions',
+    ParentRelationship.RelationshipChild,
+    ...revisions,
+  );
+
+  return builder;
+}
+
+const denseBuilder = generateMockDenseRevisionsViewModel();
+export const DenseRevisions: Story = {
+  args: {
+    chartViewModel: denseBuilder.getChartViewModel(),
+    rulerViewModel: denseBuilder.getRulerViewModel(window.innerWidth),
+    activeLogsIndices: denseBuilder.getAllActiveLogIndices(),
+    pixelsPerMs: window.innerWidth / (200 * 10),
+  },
+};

web/src/assets/revision-v2.vertex.glsl

@@ -3,7 +3,7 @@ precision highp float;
 precision highp int;
 
 #define MAX_REVISION_INDEX_DIGITS 5
-#define MIN_LEFT_REVISION_LOCATION -300.0
+#define MIN_LEFT_REVISION_LOCATION 300.0
 
 #include "v2.shared.glsl"
 #include "revision-v2.shared.glsl"
@@ -54,7 +54,7 @@ void main(){
   // 1. Calculate relative time difference from the viewport left edge.
   // Caps the time.xy with the time calculated from the screen space value not to subtract very small value and cause float precision issue on uv.
   // We can ignore the edge case that minTime could be negative because vs.leftEdgeTime should be enough larger than 0.(It's unix time)
-  uvec2 minTime = vs.leftEdgeTime - uvec2(MIN_LEFT_REVISION_LOCATION / float(vs.pixelsPerMs) / 1000.0, 1e10-1.0); // y component should always larger than time.y
+  uvec2 minTime = uvec2(vs.leftEdgeTime.x -  uint(max(1.0,MIN_LEFT_REVISION_LOCATION / float(vs.pixelsPerMs) / 1000.0)), 0);
   uvec2 cappedTime = max(time.xy, minTime);
   ivec2 leftEdgeRelativeTime = ivec2(cappedTime.xy - vs.leftEdgeTime);
   ivec2 durationTime = ivec2(time.zw - cappedTime.xy);