add Brush Designer ViewModel, preview, and app wiring

.gitignore

@@ -15,3 +15,4 @@
 .externalNativeBuild
 .cxx
 local.properties
+ink-proto/bin/

app/build.gradle.kts

@@ -164,6 +164,9 @@ dependencies {
     //Protobuf
     implementation(project(":ink-proto"))
     implementation(libs.protobuf.javalite)
+
+    //Color Picker
+    implementation(libs.compose.color.picker.android)
 }
 java {
     toolchain {

app/src/androidTest/java/com/example/cahier/CahierListDetailTest.kt

@@ -1,3 +1,20 @@
+/*
+ * Copyright 2026 Google LLC. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
 package com.example.cahier
 
 import androidx.compose.runtime.Composable
@@ -28,7 +45,7 @@ class CahierListDetailTest {
             DeviceConfigurationOverride(
                 DeviceConfigurationOverride.ForcedSize(compatWidthWindow)
             ) {
-                HomeContent()
+                HomeContent(forceCompact = true)
             }
         }
 
@@ -42,7 +59,7 @@ class CahierListDetailTest {
             DeviceConfigurationOverride(
                 DeviceConfigurationOverride.ForcedSize(mediumWidthWindow)
             ) {
-                HomeContent()
+                HomeContent(forceCompact = false)
             }
         }
 
@@ -62,11 +79,12 @@ class CahierListDetailTest {
     )
 
     @Composable
-    private fun HomeContent() {
+    private fun HomeContent(forceCompact: Boolean) {
         HomePane(
             navigateToCanvas = { _ -> },
             navigateToDrawingCanvas = { _ -> },
             navigateUp = {},
+            forceCompact = forceCompact,
             homeScreenViewModel = fakeViewModel
         )
     }

app/src/androidTest/java/com/example/cahier/developer/brushdesigner/viewmodel/BrushDesignerViewModelTest.kt

@@ -0,0 +1,155 @@
+package com.example.cahier.developer.brushdesigner.viewmodel
+
+import android.content.Context
+import android.graphics.Bitmap
+import androidx.test.core.app.ApplicationProvider
+import com.example.cahier.developer.brushdesigner.data.BrushDesignerRepository
+import com.example.cahier.developer.brushdesigner.data.CustomBrushDao
+import dagger.hilt.android.testing.HiltAndroidRule
+import dagger.hilt.android.testing.HiltAndroidTest
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.test.setMain
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import javax.inject.Inject
+
+@OptIn(ExperimentalCoroutinesApi::class)
+@HiltAndroidTest
+class BrushDesignerViewModelTest {
+
+    @get:Rule
+    var hiltRule = HiltAndroidRule(this)
+
+    private val testDispatcher = UnconfinedTestDispatcher()
+
+    @Inject
+    lateinit var customBrushDao: CustomBrushDao
+
+    @Inject
+    lateinit var repository: BrushDesignerRepository
+
+    private lateinit var viewModel: BrushDesignerViewModel
+
+    @Before
+    fun setup() {
+        hiltRule.inject()
+        Dispatchers.setMain(testDispatcher)
+
+        val context = ApplicationProvider.getApplicationContext<Context>()
+        viewModel = BrushDesignerViewModel(context, repository, customBrushDao)
+    }
+
+    @After
+    fun tearDown() {
+        Dispatchers.resetMain()
+    }
+
+    @Test
+    fun updateTip_modifies_correct_coat_index() = runTest {
+        assertEquals(
+            1.0f,
+            viewModel.activeBrushProto.value.getCoats(0).tip.scaleX,
+            0.01f
+        )
+
+        viewModel.updateTip { it.setScaleX(2.5f) }
+
+        assertEquals(
+            2.5f,
+            viewModel.activeBrushProto.value.getCoats(0).tip.scaleX,
+            0.01f
+        )
+    }
+
+    @Test
+    fun addBehavior_stacks_multiple_rules() = runTest {
+        viewModel.clearBehaviors()
+        assertEquals(
+            0,
+            viewModel.activeBrushProto.value.getCoats(0).tip.behaviorsCount
+        )
+
+        val node1 = ink.proto.BrushBehavior.Node.newBuilder().setConstantNode(
+            ink.proto.BrushBehavior.ConstantNode.newBuilder().setValue(1f)
+        ).build()
+        viewModel.addBehavior(listOf(node1))
+
+        val node2 = ink.proto.BrushBehavior.Node.newBuilder().setConstantNode(
+            ink.proto.BrushBehavior.ConstantNode.newBuilder().setValue(2f)
+        ).build()
+        viewModel.addBehavior(listOf(node2))
+
+        val behaviors = viewModel.activeBrushProto.value.getCoats(0).tip.behaviorsList
+        assertEquals(2, behaviors.size)
+    }
+
+    @Test
+    fun addNewCoat_increments_count_and_switches_selection() = runTest {
+        assertEquals(1, viewModel.activeBrushProto.value.coatsCount)
+        assertEquals(0, viewModel.selectedCoatIndex.value)
+
+        viewModel.addNewCoat()
+
+        assertEquals(2, viewModel.activeBrushProto.value.coatsCount)
+        assertEquals(1, viewModel.selectedCoatIndex.value)
+    }
+
+    @Test
+    fun saveToPalette_persists_to_dao() = runTest {
+        val brushName = "Test Persistence Brush"
+        viewModel.updateClientBrushFamilyId("test-id")
+
+        viewModel.saveToPalette(brushName).join()
+
+        val savedBrushes = customBrushDao.getAllCustomBrushes().first()
+        assertTrue(savedBrushes.any { it.name == brushName })
+    }
+
+    @Test
+    fun previewBrushFamily_is_null_on_invalid_proto() = runTest {
+        val invalidRepo = BrushDesignerRepository()
+        invalidRepo.updateActiveBrushProto(ink.proto.BrushFamily.newBuilder().build())
+
+        val vm = BrushDesignerViewModel(
+            ApplicationProvider.getApplicationContext(),
+            invalidRepo,
+            customBrushDao
+        )
+
+        assertNull(vm.previewBrushFamily.value)
+    }
+
+    @Test
+    fun setTextureStore_immediately_syncs_proto_textures() = runTest {
+        val context = ApplicationProvider.getApplicationContext<Context>()
+        val testTextureId = "test-texture"
+        val testBitmap = Bitmap.createBitmap(2, 2, Bitmap.Config.ARGB_8888)
+
+        val baos = java.io.ByteArrayOutputStream()
+        testBitmap.compress(Bitmap.CompressFormat.PNG, 100, baos)
+        val textureBytes = com.google.protobuf.ByteString.copyFrom(baos.toByteArray())
+
+        val protoWithTexture = viewModel.activeBrushProto.value.toBuilder()
+            .putTextureIdToBitmap(testTextureId, textureBytes)
+            .build()
+        repository.updateActiveBrushProto(protoWithTexture)
+
+        val store = com.example.cahier.core.ui.CahierTextureBitmapStore(context)
+        assertNull(store[testTextureId])
+
+        viewModel.setTextureStore(store)
+
+        assertNotNull(store[testTextureId])
+    }
+}

app/src/main/java/com/example/cahier/core/navigation/CahierNavGraph.kt

@@ -1,19 +1,17 @@
 /*
+ * Copyright 2025 Google LLC. All rights reserved.
  *
- *  * Copyright 2025 Google LLC. All rights reserved.
- *  *
- *  * Licensed under the Apache License, Version 2.0 (the "License");
- *  * you may not use this file except in compliance with the License.
- *  * You may obtain a copy of the License at
- *  *
- *  *     http://www.apache.org/licenses/LICENSE-2.0
- *  *
- *  * Unless required by applicable law or agreed to in writing, software
- *  * distributed under the License is distributed on an "AS IS" BASIS,
- *  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- *  * See the License for the specific language governing permissions and
- *  * limitations under the License.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
 package com.example.cahier.core.navigation
@@ -26,6 +24,7 @@ import androidx.navigation.NavType
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.navArgument
+import com.example.cahier.developer.brushdesigner.ui.BrushDesignerScreen
 import com.example.cahier.features.drawing.DrawingCanvas
 import com.example.cahier.features.home.HomeDestination
 import com.example.cahier.features.home.HomePane
@@ -54,7 +53,11 @@ fun CahierNavHost(
                 navigateUp = {
                     navController.navigateUp()
                 },
-            )
+                navigateToBrushDesigner = {
+                    navController.navigate(BrushDesignerDestination.route)
+                },
+
+                )
         }
         composable(
             route = TextCanvasDestination.routeWithArgs,
@@ -76,6 +79,12 @@ fun CahierNavHost(
                 navigateUp = { navController.navigateUp() },
             )
         }
+        composable(route = BrushDesignerDestination.route) {
+            BrushDesignerScreen(
+                onNavigateUp = { navController.navigateUp() }
+            )
+        }
+
     }
 }
 
@@ -90,4 +99,8 @@ object DrawingCanvasDestination : NavigationDestination {
     override val route = "drawing_canvas"
     const val NOTE_ID_ARG = "noteId"
     val routeWithArgs = "$route/{$NOTE_ID_ARG}"
-}
+}
+
+object BrushDesignerDestination : NavigationDestination {
+    override val route = "brush_designer"
+}

app/src/main/java/com/example/cahier/core/ui/CahierTextureBitmapStore.kt

@@ -1,3 +1,20 @@
+/*
+ * Copyright 2026 Google LLC. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
 package com.example.cahier.core.ui
 
 import android.content.Context

app/src/main/java/com/example/cahier/core/ui/theme/Color.kt

@@ -1,19 +1,17 @@
 /*
+ * Copyright 2025 Google LLC. All rights reserved.
  *
- *  * Copyright 2025 Google LLC. All rights reserved.
- *  *
- *  * Licensed under the Apache License, Version 2.0 (the "License");
- *  * you may not use this file except in compliance with the License.
- *  * You may obtain a copy of the License at
- *  *
- *  *     http://www.apache.org/licenses/LICENSE-2.0
- *  *
- *  * Unless required by applicable law or agreed to in writing, software
- *  * distributed under the License is distributed on an "AS IS" BASIS,
- *  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- *  * See the License for the specific language governing permissions and
- *  * limitations under the License.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
 package com.example.cahier.core.ui.theme
@@ -26,4 +24,11 @@ val Pink80 = Color(0xFFEFB8C8)
 
 val Purple40 = Color(0xFF6650a4)
 val PurpleGrey40 = Color(0xFF625b71)
-val Pink40 = Color(0xFF7D5260)
+val Pink40 = Color(0xFF7D5260)
+
+// Brush Designer: color picker presets
+val BrushBlack = Color(0xFF000000)
+val BrushRed = Color(0xFFFF0000)
+val BrushBlue = Color(0xFF0000FF)
+val BrushGreen = Color(0xFF00FF00)
+val BrushYellow = Color(0xFFFFFF00)