[widget Audit] toga.ScrollContainer

android/src/toga_android/container.py

@@ -0,0 +1,54 @@
+from .libs.android.widget import RelativeLayout, RelativeLayout__LayoutParams
+
+
+class Container:
+    def init_container(self, native_parent):
+        self.width = self.height = 0
+
+        context = native_parent.getContext()
+        self.native_content = RelativeLayout(context)
+        native_parent.addView(self.native_content)
+
+        self.dpi = context.getResources().getDisplayMetrics().densityDpi
+        # Toga needs to know how the current DPI compares to the platform default,
+        # which is 160: https://developer.android.com/training/multiscreen/screendensities
+        self.baseline_dpi = 160
+        self.scale = self.dpi / self.baseline_dpi
+
+    def set_content(self, widget):
+        self.clear_content()
+        if widget:
+            widget.container = self
+
+    def clear_content(self):
+        if self.interface.content:
+            self.interface.content._impl.container = None
+
+    def resize_content(self, width, height):
+        if (self.width, self.height) != (width, height):
+            self.width, self.height = (width, height)
+            if self.interface.content:
+                self.interface.content.refresh()
+
+    def refreshed(self):
+        # We must use the correct LayoutParams class, but we don't know what that class
+        # is, so reuse the existing object. Calling the constructor of type(lp) is also
+        # an option, but would probably be less safe because a subclass might change the
+        # meaning of the (int, int) constructor.
+        lp = self.native_content.getLayoutParams()
+        layout = self.interface.content.layout
+        lp.width = max(self.width, layout.width)
+        lp.height = max(self.height, layout.height)
+        self.native_content.setLayoutParams(lp)
+
+    def add_content(self, widget):
+        self.native_content.addView(widget.native)
+
+    def remove_content(self, widget):
+        self.native_content.removeView(widget.native)
+
+    def set_content_bounds(self, widget, x, y, width, height):
+        lp = RelativeLayout__LayoutParams(width, height)
+        lp.topMargin = y
+        lp.leftMargin = x
+        widget.native.setLayoutParams(lp)

android/src/toga_android/libs/android/view.py

@@ -10,6 +10,7 @@
 ViewGroup__LayoutParams = JavaClass("android/view/ViewGroup$LayoutParams")
 View__MeasureSpec = JavaClass("android/view/View$MeasureSpec")
 View__OnFocusChangeListener = JavaInterface("android/view/View$OnFocusChangeListener")
+View__OnScrollChangeListener = JavaInterface("android/view/View$OnScrollChangeListener")
 View__OnTouchListener = JavaInterface("android/view/View$OnTouchListener")
 ViewTreeObserver__OnGlobalLayoutListener = JavaInterface(
     "android/view/ViewTreeObserver$OnGlobalLayoutListener"

android/src/toga_android/widgets/base.py

@@ -41,7 +41,6 @@ def __init__(self, interface):
         self.interface = interface
         self.interface._impl = self
         self._container = None
-        self.viewport = None
         self.native = None
         self._native_activity = _get_activity()
         self.create()
@@ -65,25 +64,30 @@ def container(self):
 
     @container.setter
     def container(self, container):
-        if self.container:
-            assert container is None, "Widget already has a container"
-
-            # container is set to None, removing self from the container.native
-            self._container.native.removeView(self.native)
-            self._container.native.invalidate()
-            self._container = None
-        elif container:
-            self._container = container
-            # When initially setting the container and adding widgets to the container,
-            # we provide no `LayoutParams`. Those are promptly added when Toga
-            # calls `widget.rehint()` and `widget.set_bounds()`.
-            self._container.native.addView(self.native)
+        if self._container:
+            self._container.remove_content(self)
+
+        self._container = container
+        if container:
+            container.add_content(self)
 
         for child in self.interface.children:
             child._impl.container = container
 
         self.rehint()
 
+    @property
+    def viewport(self):
+        return self._container
+
+    # Convert CSS pixels to native pixels
+    def scale_in(self, value):
+        return int(round(value * self.container.scale))
+
+    # Convert native pixels to CSS pixels
+    def scale_out(self, value):
+        return int(round(value / self.container.scale))
+
     def get_enabled(self):
         return self.native.isEnabled()
 
@@ -103,9 +107,7 @@ def set_tab_index(self, tab_index):
     # APPLICATOR
 
     def set_bounds(self, x, y, width, height):
-        if self.container:
-            # Ask the container widget to set our bounds.
-            self.container.set_child_bounds(self, x, y, width, height)
+        self.container.set_content_bounds(self, x, y, width, height)
 
     def set_hidden(self, hidden):
         if hidden:
@@ -160,11 +162,7 @@ def set_color(self, color):
     # INTERFACE
 
     def add_child(self, child):
-        if self.viewport:
-            # we are the top level widget
-            child.container = self
-        else:
-            child.container = self.container
+        child.container = self.container
 
     def insert_child(self, index, child):
         self.add_child(child)

android/src/toga_android/widgets/box.py

@@ -1,24 +1,14 @@
 from travertino.size import at_least
 
 from ..libs.activity import MainActivity
-from ..libs.android.widget import RelativeLayout, RelativeLayout__LayoutParams
+from ..libs.android.widget import RelativeLayout
 from .base import Widget
 
 
 class Box(Widget):
     def create(self):
         self.native = RelativeLayout(MainActivity.singletonThis)
 
-    def set_child_bounds(self, widget, x, y, width, height):
-        # We assume `widget.native` has already been added to this `RelativeLayout`.
-        #
-        # We use `topMargin` and `leftMargin` to perform absolute layout. Not very
-        # relative, but that's how we do it.
-        layout_params = RelativeLayout__LayoutParams(width, height)
-        layout_params.topMargin = y
-        layout_params.leftMargin = x
-        self.native.updateViewLayout(widget.native, layout_params)
-
     def set_background_color(self, value):
         self.set_background_simple(value)
 

android/src/toga_android/widgets/canvas.py

@@ -64,33 +64,29 @@ def closed_path(self, x, y, path, *args, **kwargs):
         path.close()
 
     def move_to(self, x, y, path, *args, **kwargs):
-        path.moveTo(
-            self.container.viewport.scale * x, self.container.viewport.scale * y
-        )
+        path.moveTo(self.container.scale * x, self.container.scale * y)
 
     def line_to(self, x, y, path, *args, **kwargs):
-        path.lineTo(
-            self.container.viewport.scale * x, self.container.viewport.scale * y
-        )
+        path.lineTo(self.container.scale * x, self.container.scale * y)
 
     # Basic shapes
 
     def bezier_curve_to(self, cp1x, cp1y, cp2x, cp2y, x, y, path, *args, **kwargs):
         path.cubicTo(
-            cp1x * self.container.viewport.scale,
-            cp1y * self.container.viewport.scale,
-            cp2x * self.container.viewport.scale,
-            cp2y * self.container.viewport.scale,
-            x * self.container.viewport.scale,
-            y * self.container.viewport.scale,
+            cp1x * self.container.scale,
+            cp1y * self.container.scale,
+            cp2x * self.container.scale,
+            cp2y * self.container.scale,
+            x * self.container.scale,
+            y * self.container.scale,
         )
 
     def quadratic_curve_to(self, cpx, cpy, x, y, path, *args, **kwargs):
         path.quadTo(
-            cpx * self.container.viewport.scale,
-            cpy * self.container.viewport.scale,
-            x * self.container.viewport.scale,
-            y * self.container.viewport.scale,
+            cpx * self.container.scale,
+            cpy * self.container.scale,
+            x * self.container.scale,
+            y * self.container.scale,
         )
 
     def arc(
@@ -100,10 +96,10 @@ def arc(
         if anticlockwise:
             sweep_angle -= math.radians(360)
         path.arcTo(
-            self.container.viewport.scale * (x - radius),
-            self.container.viewport.scale * (y - radius),
-            self.container.viewport.scale * (x + radius),
-            self.container.viewport.scale * (y + radius),
+            self.container.scale * (x - radius),
+            self.container.scale * (y - radius),
+            self.container.scale * (x + radius),
+            self.container.scale * (y + radius),
             math.degrees(startangle),
             math.degrees(sweep_angle),
             False,
@@ -128,28 +124,28 @@ def ellipse(
             sweep_angle -= math.radians(360)
         ellipse_path = Path()
         ellipse_path.addArc(
-            self.container.viewport.scale * (x - radiusx),
-            self.container.viewport.scale * (y - radiusy),
-            self.container.viewport.scale * (x + radiusx),
-            self.container.viewport.scale * (y + radiusy),
+            self.container.scale * (x - radiusx),
+            self.container.scale * (y - radiusy),
+            self.container.scale * (x + radiusx),
+            self.container.scale * (y + radiusy),
             math.degrees(startangle),
             math.degrees(sweep_angle),
         )
         rotation_matrix = Matrix()
         rotation_matrix.postRotate(
             math.degrees(rotation),
-            self.container.viewport.scale * x,
-            self.container.viewport.scale * y,
+            self.container.scale * x,
+            self.container.scale * y,
         )
         ellipse_path.transform(rotation_matrix)
         path.addPath(ellipse_path)
 
     def rect(self, x, y, width, height, path, *args, **kwargs):
         path.addRect(
-            self.container.viewport.scale * x,
-            self.container.viewport.scale * y,
-            self.container.viewport.scale * (x + width),
-            self.container.viewport.scale * (y + height),
+            self.container.scale * x,
+            self.container.scale * y,
+            self.container.scale * (x + width),
+            self.container.scale * (y + height),
             Path__Direction.CW,
         )
 
@@ -171,7 +167,7 @@ def fill(self, color, fill_rule, preserve, path, canvas, *args, **kwargs):
     def stroke(self, color, line_width, line_dash, path, canvas, *args, **kwargs):
         draw_paint = Paint()
         draw_paint.setAntiAlias(True)
-        draw_paint.setStrokeWidth(self.container.viewport.scale * line_width)
+        draw_paint.setStrokeWidth(self.container.scale * line_width)
         draw_paint.setStyle(Paint__Style.STROKE)
         if color is None:
             a, r, g, b = 255, 0, 0, 0
@@ -180,7 +176,7 @@ def stroke(self, color, line_width, line_dash, path, canvas, *args, **kwargs):
         if line_dash is not None:
             draw_paint.setPathEffect(
                 DashPathEffect(
-                    [(self.container.viewport.scale * float(d)) for d in line_dash], 0.0
+                    [(self.container.scale * float(d)) for d in line_dash], 0.0
                 )
             )
         draw_paint.setARGB(a, r, g, b)
@@ -197,9 +193,7 @@ def scale(self, sx, sy, canvas, *args, **kwargs):
         canvas.scale(float(sx), float(sy))
 
     def translate(self, tx, ty, canvas, *args, **kwargs):
-        canvas.translate(
-            self.container.viewport.scale * tx, self.container.viewport.scale * ty
-        )
+        canvas.translate(self.container.scale * tx, self.container.scale * ty)
 
     def reset_transform(self, canvas, *args, **kwargs):
         canvas.restore()