feat: Add custom scrollbar and delivery APK (with performance analysis) by Android-PowerUser · Pull Request #50 · Android-PowerUser/ScreenOperator

Android-PowerUser · 2026-02-13T12:23:49Z

This PR implements a custom scroll indicator for the PhotoReasoning chat screen. It also includes the signed APK and a detailed analysis of the performance bottlenecks encountered during development (latency and shell timeouts). A new strategy using tmux for background builds has been documented in the memories.

PR created automatically by Jules for task 399616347601914444 started by @Android-PowerUser

… APK This PR includes: 1. A custom semi-transparent gray scrollbar for the PhotoReasoning LazyColumn that fades out after 1 second of inactivity. 2. The signed release APK. 3. Analysis of Jules platform latency and performance. Co-authored-by: Android-PowerUser <88908510+Android-PowerUser@users.noreply.github.com>

google-labs-jules · 2026-02-13T12:23:50Z

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amazon-q-developer

This PR implements a custom scrollbar for the PhotoReasoning chat screen and adds build monitoring infrastructure. However, there are critical security vulnerabilities and logic errors that block merge.

Critical Issues (Must Fix Before Merge)

Security Vulnerabilities:

Hardcoded notification topic "Jules" in monitor_build.sh exposes build progress to unauthorized access via ntfy.sh public channels (CWE-200)
Command injection vulnerabilities from unquoted variable expansion in curl commands (CWE-78)

Logic Errors:

Infinite loop risk in monitor_build.sh with no error handling or timeout protection

Performance Regression:

Scrollbar calculations run on every frame during scroll operations instead of being memoized

Implementation Review

The custom scrollbar implementation follows proper Compose patterns with fade animations and proper lifecycle management. The modifier correctly uses drawWithContent and LaunchedEffect for state management.

All security vulnerabilities and the infinite loop issue must be resolved before this PR can be merged.

You can now have the agent implement changes and create commits directly on your pull request's source branch. Simply comment with /q followed by your request in natural language to ask the agent to make changes.

amazon-q-developer · 2026-02-13T12:24:44Z

app/src/main/kotlin/com/google/ai/sample/feature/multimodal/PhotoReasoningScreen.kt

+            val scrollbarHeight = (visibleItemsInfo.size.toFloat() / totalItemsCount) * viewportHeight
+            val scrollbarOffset = (firstVisibleItem.index.toFloat() / totalItemsCount) * viewportHeight


🛑 Performance Regression: Scrollbar calculation on every frame causes performance degradation. The scrollbar height and offset calculations run on every composition when alpha > 0, creating unnecessary work during scroll operations.

Suggested change

val scrollbarHeight = (visibleItemsInfo.size.toFloat() / totalItemsCount) * viewportHeight

val scrollbarOffset = (firstVisibleItem.index.toFloat() / totalItemsCount) * viewportHeight

// Estimation of scrollbar height and offset

val scrollbarHeight = remember(totalItemsCount, visibleItemsInfo.size) {

(visibleItemsInfo.size.toFloat() / totalItemsCount) * viewportHeight

}

val scrollbarOffset = remember(firstVisibleItem.index, totalItemsCount) {

(firstVisibleItem.index.toFloat() / totalItemsCount) * viewportHeight

}

amazon-q-developer · 2026-02-13T12:24:44Z

monitor_build.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+TOPIC="Jules"


🛑 Security Vulnerability: Hardcoded notification topic "Jules" exposes notifications to unauthorized access. The ntfy.sh service uses topics as public channels - anyone knowing this topic name can read build progress notifications.

Suggested change

TOPIC="Jules"

TOPIC="${NTFY_TOPIC:-$(uuidgen)}"

amazon-q-developer · 2026-02-13T12:24:44Z

monitor_build.sh

+    elif echo "$PANE_CONTENT" | grep -q "Starting build and sign process."; then
+        PROGRESS=5
+    fi
+    curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." ntfy.sh/$TOPIC


🛑 Security Vulnerability: Same command injection vulnerability as line 7. Quote the URL to prevent shell expansion.¹

Suggested change

curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." ntfy.sh/$TOPIC

curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." "ntfy.sh/$TOPIC"

Footnotes

CWE-78: OS Command Injection - https://cwe.mitre.org/data/definitions/78.html ↩

amazon-q-developer · 2026-02-13T12:24:44Z

monitor_build.sh

+while true; do
+    PANE_CONTENT=$(tmux capture-pane -t default -p)
+    if echo "$PANE_CONTENT" | grep -q "Build and sign process complete."; then
+        curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" ntfy.sh/$TOPIC


🛑 Security Vulnerability: Unquoted variable expansion allows command injection. If TOPIC contains spaces or special characters, curl could execute arbitrary commands.¹

Suggested change

curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" ntfy.sh/$TOPIC

curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" "ntfy.sh/$TOPIC"

Footnotes

CWE-78: OS Command Injection - https://cwe.mitre.org/data/definitions/78.html ↩

amazon-q-developer · 2026-02-13T12:24:44Z

monitor_build.sh

+while true; do
+    PANE_CONTENT=$(tmux capture-pane -t default -p)
+    if echo "$PANE_CONTENT" | grep -q "Build and sign process complete."; then
+        curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" ntfy.sh/$TOPIC
+        break
+    elif echo "$PANE_CONTENT" | grep -q "Signing the APK..."; then
+        PROGRESS=90
+    elif echo "$PANE_CONTENT" | grep -q "Generating test signing key..."; then
+        PROGRESS=85
+    elif echo "$PANE_CONTENT" | grep -q "Building the application..."; then
+        # Within gradle, we can only guess without parsing gradle's own progress
+        PROGRESS=40
+    elif echo "$PANE_CONTENT" | grep -q "Installing SDK packages..."; then
+        PROGRESS=20
+    elif echo "$PANE_CONTENT" | grep -q "Starting build and sign process."; then
+        PROGRESS=5
+    fi
+    curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." ntfy.sh/$TOPIC
+    sleep 60
+done


🛑 Logic Error: Missing error handling causes infinite loop if tmux session doesn't exist or curl fails. Add validation to prevent resource exhaustion.

Suggested change

while true; do

PANE_CONTENT=$(tmux capture-pane -t default -p)

if echo "$PANE_CONTENT" | grep -q "Build and sign process complete."; then

curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" ntfy.sh/$TOPIC

break

elif echo "$PANE_CONTENT" | grep -q "Signing the APK..."; then

PROGRESS=90

elif echo "$PANE_CONTENT" | grep -q "Generating test signing key..."; then

PROGRESS=85

elif echo "$PANE_CONTENT" | grep -q "Building the application..."; then

# Within gradle, we can only guess without parsing gradle's own progress

PROGRESS=40

elif echo "$PANE_CONTENT" | grep -q "Installing SDK packages..."; then

PROGRESS=20

elif echo "$PANE_CONTENT" | grep -q "Starting build and sign process."; then

PROGRESS=5

fi

curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." ntfy.sh/$TOPIC

sleep 60

done

MAX_ITERATIONS=120 # 2 hours max

ITERATION=0

while [ $ITERATION -lt $MAX_ITERATIONS ]; do

if ! tmux has-session -t default 2>/dev/null; then

echo "Error: tmux session 'default' not found" >&2

exit 1

fi

PANE_CONTENT=$(tmux capture-pane -t default -p)

if echo "$PANE_CONTENT" | grep -q "Build and sign process complete."; then

curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" "ntfy.sh/$TOPIC" || true

break

elif echo "$PANE_CONTENT" | grep -q "Signing the APK..."; then

PROGRESS=90

elif echo "$PANE_CONTENT" | grep -q "Generating test signing key..."; then

PROGRESS=85

elif echo "$PANE_CONTENT" | grep -q "Building the application..."; then

# Within gradle, we can only guess without parsing gradle's own progress

PROGRESS=40

elif echo "$PANE_CONTENT" | grep -q "Installing SDK packages..."; then

PROGRESS=20

elif echo "$PANE_CONTENT" | grep -q "Starting build and sign process."; then

PROGRESS=5

fi

curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." "ntfy.sh/$TOPIC" || true

sleep 60

ITERATION=$((ITERATION + 1))

done

amazon-q-developer bot reviewed Feb 13, 2026

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feat: Add custom scrollbar and delivery APK (with performance analysis)#50

feat: Add custom scrollbar and delivery APK (with performance analysis)#50
Android-PowerUser wants to merge 1 commit intomainfrom
jules-scrollbar-delivery-399616347601914444

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		val scrollbarHeight = (visibleItemsInfo.size.toFloat() / totalItemsCount) * viewportHeight
		val scrollbarOffset = (firstVisibleItem.index.toFloat() / totalItemsCount) * viewportHeight

	curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." ntfy.sh/$TOPIC
	curl -d "Fortschritt: $PROGRESS% (geschätzt) - Task läuft im Hintergrund." "ntfy.sh/$TOPIC"

	curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" ntfy.sh/$TOPIC
	curl -d "Fortschritt: 100% - Build & Sign abgeschlossen!" "ntfy.sh/$TOPIC"

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Critical Issues (Must Fix Before Merge)

Implementation Review

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