feat(mediaviewer): show the position, add forward and draw actions to the media viewer

app/build.gradle.kts

@@ -41,6 +41,7 @@ val androidxTestVersion = "1.5.0"
 val media3Version = "1.11.1"
 val coroutinesVersion = "1.11.0"
 val mockitoKotlinVersion = "6.4.0"
+val cameraXVersion = "1.6.1"
 
 android {
     compileSdk = 37
@@ -244,6 +245,12 @@ dependencies {
     implementation("androidx.lifecycle:lifecycle-common:$lifecycleVersion")
     implementation("androidx.lifecycle:lifecycle-viewmodel-compose:$lifecycleVersion")
 
+    implementation("androidx.camera:camera-core:$cameraXVersion")
+    implementation("androidx.camera:camera-camera2:$cameraXVersion")
+    implementation("androidx.camera:camera-lifecycle:$cameraXVersion")
+    implementation("androidx.camera:camera-video:$cameraXVersion")
+    implementation("androidx.camera:camera-view:$cameraXVersion")
+
     implementation("androidx.biometric:biometric:1.1.0")
 
     implementation("io.reactivex.rxjava2:rxandroid:2.1.1")

app/src/main/AndroidManifest.xml

@@ -65,6 +65,7 @@
         android:maxSdkVersion="32" />
     <uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
     <uses-permission android:name="android.permission.READ_MEDIA_VIDEO" />
+    <uses-permission android:name="android.permission.READ_MEDIA_VISUAL_USER_SELECTED" />
     <uses-permission android:name="android.permission.READ_MEDIA_AUDIO" />
 
     <uses-permission android:name="android.permission.WAKE_LOCK" />
@@ -191,6 +192,12 @@
             </intent-filter>
         </activity>
 
+        <activity
+            android:name=".camera.CaptureActivity"
+            android:configChanges="orientation|keyboardHidden|screenSize|screenLayout"
+            android:exported="false"
+            android:theme="@style/FullScreenImageTheme" />
+
         <activity
             android:name=".chat.ChatActivity"
             android:theme="@style/AppTheme.DisplayCutout" />

app/src/main/java/com/nextcloud/talk/attachmentpreview/AttachmentEditLogic.kt

@@ -0,0 +1,136 @@
+/*
+ * Nextcloud Talk - Android Client
+ *
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+package com.nextcloud.talk.attachmentpreview
+
+import kotlin.math.ceil
+
+/*
+ * Pure, Android-free helpers behind the attachment preview editing features, kept apart from the
+ * UI so they can be covered by plain JVM unit tests.
+ */
+
+private const val EDITED_SUFFIX = "_edited_"
+private const val SHARED_URI_SEGMENT = "shared_attachments"
+private val editedSuffixRegex = Regex("${EDITED_SUFFIX}[0-9-]+$")
+private const val MAX_DECODE_PIXELS = 20_000_000L
+
+/** A point on the displayed image, in 0..1 of the image's width/height (resolution independent). */
+internal data class NormalizedPoint(val x: Float, val y: Float)
+
+/** One finger-down..finger-up brush stroke. [widthFraction] is the brush width relative to the image width. */
+internal data class DrawStroke(val colorArgb: Int, val widthFraction: Float, val points: List<NormalizedPoint>)
+
+/** Where an image of a given aspect ratio lands when fitted (letterboxed) into a view, in view pixels. */
+internal data class FitRect(val left: Float, val top: Float, val width: Float, val height: Float)
+
+/** Replaces [oldUri] by [newUri] keeping its position; returns [files] unchanged when [oldUri] is absent. */
+internal fun replaceUri(files: List<String>, oldUri: String, newUri: String): List<String> {
+    val index = files.indexOf(oldUri)
+    return if (index < 0 || oldUri == newUri) {
+        files
+    } else {
+        files.toMutableList().also { it[index] = newUri }
+    }
+}
+
+/**
+ * Toggles [uri] in the set of files excluded from sending. At least one file always stays selected,
+ * so excluding the last selected file is refused (the set is returned unchanged).
+ */
+internal fun toggleSelection(files: List<String>, unselected: Set<String>, uri: String): Set<String> =
+    when {
+        uri !in files -> unselected
+        uri in unselected -> unselected - uri
+        files.count { it !in unselected } <= 1 -> unselected
+        else -> unselected + uri
+    }
+
+/** The files that will actually be sent, in list order. */
+internal fun selectedFiles(files: List<String>, unselected: Set<String>): List<String> =
+    files.filter { it !in unselected }
+
+/**
+ * Name for the file an edit produces: the original base name without extension and without an
+ * earlier edit suffix (so repeated edits don't pile suffixes up), plus a unique [stamp].
+ */
+internal fun editedFileName(originalName: String, stamp: String, extension: String): String {
+    val base = originalName.substringBeforeLast('.', originalName).replace(editedSuffixRegex, "")
+    return "${base.ifBlank { "image" }}$EDITED_SUFFIX$stamp.$extension"
+}
+
+/** True for names produced by [editedFileName], i.e. intermediates of an earlier edit. */
+internal fun isEditedFileName(fileName: String): Boolean =
+    editedSuffixRegex.containsMatchIn(fileName.substringBeforeLast('.', fileName))
+
+/**
+ * The edited file's name when [pathSegments] of a URI under [authority] address exactly
+ * `shared_attachments/<edit-suffixed name>` in our own FileProvider; null for anything else
+ * (foreign authority, an original/camera file, a nested path). Only those are ours to delete.
+ */
+internal fun ownEditedName(authority: String?, ownAuthority: String, pathSegments: List<String>): String? {
+    val name = pathSegments.getOrNull(1)
+    val matches = authority == ownAuthority &&
+        pathSegments.size == 2 &&
+        pathSegments.first() == SHARED_URI_SEGMENT &&
+        name != null &&
+        isEditedFileName(name)
+    return if (matches) name else null
+}
+
+/**
+ * Whether drawing must turn the pixels upright instead of carrying the EXIF orientation tag over.
+ * Mirrored orientations (2/4/5/7) are not understood downstream, and PNG is not rotated by EXIF at
+ * all; only JPEG with the plain rotations 3/6/8 keeps the tag.
+ */
+internal fun rotatesPixels(png: Boolean, rotationDegrees: Int, flipped: Boolean): Boolean =
+    flipped || (png && rotationDegrees != 0)
+
+/** Output extension and whether it is PNG (lossless, keeps transparency) for a source MIME type. */
+internal fun editOutputIsPng(sourceMimeType: String?): Boolean = sourceMimeType == "image/png"
+
+/** Fits an image of [aspectRatio] (width / height) into the view like `ContentScale.Fit`, centered. */
+internal fun fitRect(viewWidth: Float, viewHeight: Float, aspectRatio: Float): FitRect {
+    val viewRatio = viewWidth / viewHeight
+    val (width, height) = if (viewRatio > aspectRatio) {
+        (viewHeight * aspectRatio) to viewHeight
+    } else {
+        viewWidth to (viewWidth / aspectRatio)
+    }
+    return FitRect((viewWidth - width) / 2f, (viewHeight - height) / 2f, width, height)
+}
+
+/** Maps a view-space touch position to the image, clamped so strokes can't leave the picture. */
+internal fun toNormalized(x: Float, y: Float, rect: FitRect): NormalizedPoint =
+    NormalizedPoint(
+        ((x - rect.left) / rect.width).coerceIn(0f, 1f),
+        ((y - rect.top) / rect.height).coerceIn(0f, 1f)
+    )
+
+/** Maps a normalized point to pixels of a bitmap of the given size. */
+internal fun toPixels(point: NormalizedPoint, bitmapWidth: Int, bitmapHeight: Int): Pair<Float, Float> =
+    (point.x * bitmapWidth) to (point.y * bitmapHeight)
+
+/** Brush width in bitmap pixels; never thinner than one pixel. */
+internal fun strokeWidthPixels(stroke: DrawStroke, bitmapWidth: Int): Float =
+    (stroke.widthFraction * bitmapWidth).coerceAtLeast(1f)
+
+/** Drops the most recent stroke ("undo"). */
+internal fun undoLast(strokes: List<DrawStroke>): List<DrawStroke> = strokes.dropLast(1)
+
+/**
+ * Power-of-two `inSampleSize` that keeps a decoded bitmap under [maxPixels]; 1 means full resolution.
+ * Only very large sources (beyond ~20 MP) are downsampled, to avoid running out of memory.
+ */
+internal fun decodeSampleSize(width: Int, height: Int, maxPixels: Long = MAX_DECODE_PIXELS): Int {
+    var sample = 1
+    var pixels = width.toLong() * height.toLong()
+    while (pixels > maxPixels) {
+        sample *= 2
+        pixels = ceil(width / sample.toDouble()).toLong() * ceil(height / sample.toDouble()).toLong()
+    }
+    return sample
+}