Add support for multi-window popups on Windows

ci/licenses_golden/excluded_files

@@ -335,6 +335,7 @@
 ../../../flutter/shell/platform/common/text_editing_delta_unittests.cc
 ../../../flutter/shell/platform/common/text_input_model_unittests.cc
 ../../../flutter/shell/platform/common/text_range_unittests.cc
+../../../flutter/shell/platform/common/windowing_unittests.cc
 ../../../flutter/shell/platform/darwin/Doxyfile
 ../../../flutter/shell/platform/darwin/common/availability_version_check_unittests.cc
 ../../../flutter/shell/platform/darwin/common/framework/Source/flutter_codecs_unittest.mm
@@ -408,6 +409,7 @@
 ../../../flutter/shell/platform/windows/direct_manipulation_unittests.cc
 ../../../flutter/shell/platform/windows/dpi_utils_unittests.cc
 ../../../flutter/shell/platform/windows/fixtures
+../../../flutter/shell/platform/windows/flutter_host_window_controller_unittests.cc
 ../../../flutter/shell/platform/windows/flutter_project_bundle_unittests.cc
 ../../../flutter/shell/platform/windows/flutter_window_unittests.cc
 ../../../flutter/shell/platform/windows/flutter_windows_engine_unittests.cc
@@ -428,6 +430,7 @@
 ../../../flutter/shell/platform/windows/text_input_plugin_unittest.cc
 ../../../flutter/shell/platform/windows/window_proc_delegate_manager_unittests.cc
 ../../../flutter/shell/platform/windows/window_unittests.cc
+../../../flutter/shell/platform/windows/windowing_handler_unittests.cc
 ../../../flutter/shell/platform/windows/windows_lifecycle_manager_unittests.cc
 ../../../flutter/shell/profiling/sampling_profiler_unittest.cc
 ../../../flutter/shell/testing

ci/licenses_golden/licenses_flutter

@@ -47454,6 +47454,8 @@ FILE: ../../../flutter/shell/platform/common/text_editing_delta.h
 FILE: ../../../flutter/shell/platform/common/text_input_model.cc
 FILE: ../../../flutter/shell/platform/common/text_input_model.h
 FILE: ../../../flutter/shell/platform/common/text_range.h
+FILE: ../../../flutter/shell/platform/common/windowing.cc
+FILE: ../../../flutter/shell/platform/common/windowing.h
 FILE: ../../../flutter/shell/platform/darwin/common/availability_version_check.cc
 FILE: ../../../flutter/shell/platform/darwin/common/availability_version_check.h
 FILE: ../../../flutter/shell/platform/darwin/common/buffer_conversions.h
@@ -48197,6 +48199,10 @@ FILE: ../../../flutter/shell/platform/windows/flutter_platform_node_delegate_win
 FILE: ../../../flutter/shell/platform/windows/flutter_platform_node_delegate_windows.h
 FILE: ../../../flutter/shell/platform/windows/flutter_project_bundle.cc
 FILE: ../../../flutter/shell/platform/windows/flutter_project_bundle.h
+FILE: ../../../flutter/shell/platform/windows/flutter_host_window.cc
+FILE: ../../../flutter/shell/platform/windows/flutter_host_window.h
+FILE: ../../../flutter/shell/platform/windows/flutter_host_window_controller.cc
+FILE: ../../../flutter/shell/platform/windows/flutter_host_window_controller.h
 FILE: ../../../flutter/shell/platform/windows/flutter_window.cc
 FILE: ../../../flutter/shell/platform/windows/flutter_window.h
 FILE: ../../../flutter/shell/platform/windows/flutter_windows.cc
@@ -48246,6 +48252,8 @@ FILE: ../../../flutter/shell/platform/windows/window_binding_handler_delegate.h
 FILE: ../../../flutter/shell/platform/windows/window_proc_delegate_manager.cc
 FILE: ../../../flutter/shell/platform/windows/window_proc_delegate_manager.h
 FILE: ../../../flutter/shell/platform/windows/window_state.h
+FILE: ../../../flutter/shell/platform/windows/windowing_handler.cc
+FILE: ../../../flutter/shell/platform/windows/windowing_handler.h
 FILE: ../../../flutter/shell/platform/windows/windows_lifecycle_manager.cc
 FILE: ../../../flutter/shell/platform/windows/windows_lifecycle_manager.h
 FILE: ../../../flutter/shell/platform/windows/windows_proc_table.cc

common/settings.h

@@ -367,6 +367,10 @@ struct Settings {
   // If true, the UI thread is the platform thread on supported
   // platforms.
   bool merged_platform_ui_thread = true;
+
+  // Enable support for multiple windows. Ignored if not supported on the
+  // platform.
+  bool enable_multi_window = false;
 };
 
 }  // namespace flutter

shell/common/switches.cc

@@ -532,6 +532,17 @@ Settings SettingsFromCommandLine(const fml::CommandLine& command_line) {
   settings.merged_platform_ui_thread = !command_line.HasOption(
       FlagForSwitch(Switch::DisableMergedPlatformUIThread));
 
+#if FML_OS_WIN
+  // Process the EnableMultiWindow switch on Windows.
+  {
+    std::string enable_multi_window_value;
+    if (command_line.GetOptionValue(FlagForSwitch(Switch::EnableMultiWindow),
+                                    &enable_multi_window_value)) {
+      settings.enable_multi_window = "true" == enable_multi_window_value;
+    }
+  }
+#endif  // FML_OS_WIN
+
   return settings;
 }
 

shell/common/switches.h

@@ -300,6 +300,10 @@ DEF_SWITCH(DisableMergedPlatformUIThread,
 DEF_SWITCH(DisableAndroidSurfaceControl,
            "disable-surface-control",
            "Disable the SurfaceControl backed swapchain even when supported.")
+DEF_SWITCH(EnableMultiWindow,
+           "enable-multi-window",
+           "Enable support for multiple windows. Ignored if not supported on "
+           "the platform.")
 DEF_SWITCHES_END
 
 void PrintUsage(const std::string& executable_name);

shell/platform/common/BUILD.gn

@@ -142,9 +142,13 @@ source_set("common_cpp_core") {
   public = [
     "geometry.h",
     "path_utils.h",
+    "windowing.h",
   ]
 
-  sources = [ "path_utils.cc" ]
+  sources = [
+    "path_utils.cc",
+    "windowing.cc",
+  ]
 
   public_configs = [ "//flutter:config" ]
 }
@@ -157,7 +161,10 @@ if (enable_unittests) {
   executable("common_cpp_core_unittests") {
     testonly = true
 
-    sources = [ "path_utils_unittests.cc" ]
+    sources = [
+      "path_utils_unittests.cc",
+      "windowing_unittests.cc",
+    ]
 
     deps = [
       ":common_cpp_core",

shell/platform/common/windowing.cc

@@ -0,0 +1,278 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/common/windowing.h"
+
+#include <algorithm>
+#include <iostream>
+
+namespace flutter {
+
+namespace {
+
+WindowPoint offset_for(WindowSize const& size,
+                       WindowPositioner::Anchor anchor) {
+  switch (anchor) {
+    case WindowPositioner::Anchor::top_left:
+      return {0, 0};
+    case WindowPositioner::Anchor::top:
+      return {-size.width / 2, 0};
+    case WindowPositioner::Anchor::top_right:
+      return {-1 * size.width, 0};
+    case WindowPositioner::Anchor::left:
+      return {0, -size.height / 2};
+    case WindowPositioner::Anchor::center:
+      return {-size.width / 2, -size.height / 2};
+    case WindowPositioner::Anchor::right:
+      return {-1 * size.width, -size.height / 2};
+    case WindowPositioner::Anchor::bottom_left:
+      return {0, -1 * size.height};
+    case WindowPositioner::Anchor::bottom:
+      return {-size.width / 2, -1 * size.height};
+    case WindowPositioner::Anchor::bottom_right:
+      return {-1 * size.width, -1 * size.height};
+    default:
+      std::cerr << "Unknown anchor value: " << static_cast<int>(anchor) << '\n';
+      std::abort();
+  }
+}
+
+WindowPoint anchor_position_for(WindowRectangle const& rect,
+                                WindowPositioner::Anchor anchor) {
+  switch (anchor) {
+    case WindowPositioner::Anchor::top_left:
+      return rect.top_left;
+    case WindowPositioner::Anchor::top:
+      return rect.top_left + WindowPoint{rect.size.width / 2, 0};
+    case WindowPositioner::Anchor::top_right:
+      return rect.top_left + WindowPoint{rect.size.width, 0};
+    case WindowPositioner::Anchor::left:
+      return rect.top_left + WindowPoint{0, rect.size.height / 2};
+    case WindowPositioner::Anchor::center:
+      return rect.top_left +
+             WindowPoint{rect.size.width / 2, rect.size.height / 2};
+    case WindowPositioner::Anchor::right:
+      return rect.top_left + WindowPoint{rect.size.width, rect.size.height / 2};
+    case WindowPositioner::Anchor::bottom_left:
+      return rect.top_left + WindowPoint{0, rect.size.height};
+    case WindowPositioner::Anchor::bottom:
+      return rect.top_left + WindowPoint{rect.size.width / 2, rect.size.height};
+    case WindowPositioner::Anchor::bottom_right:
+      return rect.top_left + WindowPoint{rect.size.width, rect.size.height};
+    default:
+      std::cerr << "Unknown anchor value: " << static_cast<int>(anchor) << '\n';
+      std::abort();
+  }
+}
+
+WindowPoint constrain_to(WindowRectangle const& r, WindowPoint const& p) {
+  return {std::clamp(p.x, r.top_left.x, r.top_left.x + r.size.width),
+          std::clamp(p.y, r.top_left.y, r.top_left.y + r.size.height)};
+}
+
+WindowPositioner::Anchor flip_anchor_x(WindowPositioner::Anchor anchor) {
+  switch (anchor) {
+    case WindowPositioner::Anchor::top_left:
+      return WindowPositioner::Anchor::top_right;
+    case WindowPositioner::Anchor::top_right:
+      return WindowPositioner::Anchor::top_left;
+    case WindowPositioner::Anchor::left:
+      return WindowPositioner::Anchor::right;
+    case WindowPositioner::Anchor::right:
+      return WindowPositioner::Anchor::left;
+    case WindowPositioner::Anchor::bottom_left:
+      return WindowPositioner::Anchor::bottom_right;
+    case WindowPositioner::Anchor::bottom_right:
+      return WindowPositioner::Anchor::bottom_left;
+    default:
+      return anchor;
+  }
+}
+
+WindowPositioner::Anchor flip_anchor_y(WindowPositioner::Anchor anchor) {
+  switch (anchor) {
+    case WindowPositioner::Anchor::top_left:
+      return WindowPositioner::Anchor::bottom_left;
+    case WindowPositioner::Anchor::top:
+      return WindowPositioner::Anchor::bottom;
+    case WindowPositioner::Anchor::top_right:
+      return WindowPositioner::Anchor::bottom_right;
+    case WindowPositioner::Anchor::bottom_left:
+      return WindowPositioner::Anchor::top_left;
+    case WindowPositioner::Anchor::bottom:
+      return WindowPositioner::Anchor::top;
+    case WindowPositioner::Anchor::bottom_right:
+      return WindowPositioner::Anchor::top_right;
+    default:
+      return anchor;
+  }
+}
+
+WindowPoint flip_offset_x(WindowPoint const& p) {
+  return {-1 * p.x, p.y};
+}
+
+WindowPoint flip_offset_y(WindowPoint const& p) {
+  return {p.x, -1 * p.y};
+}
+
+}  // namespace
+
+WindowRectangle PlaceWindow(WindowPositioner const& positioner,
+                            WindowSize child_size,
+                            WindowRectangle const& anchor_rect,
+                            WindowRectangle const& parent_rect,
+                            WindowRectangle const& output_rect) {
+  WindowRectangle default_result;
+
+  {
+    WindowPoint const result =
+        constrain_to(parent_rect, anchor_position_for(
+                                      anchor_rect, positioner.parent_anchor) +
+                                      positioner.offset) +
+        offset_for(child_size, positioner.child_anchor);
+
+    if (output_rect.contains({result, child_size})) {
+      return WindowRectangle{result, child_size};
+    }
+
+    default_result = WindowRectangle{result, child_size};
+  }
+
+  if (static_cast<int>(positioner.constraint_adjustment) &
+      static_cast<int>(WindowPositioner::ConstraintAdjustment::flip_x)) {
+    WindowPoint const result =
+        constrain_to(parent_rect,
+                     anchor_position_for(
+                         anchor_rect, flip_anchor_x(positioner.parent_anchor)) +
+                         flip_offset_x(positioner.offset)) +
+        offset_for(child_size, flip_anchor_x(positioner.child_anchor));
+
+    if (output_rect.contains({result, child_size})) {
+      return WindowRectangle{result, child_size};
+    }
+  }
+
+  if (static_cast<int>(positioner.constraint_adjustment) &
+      static_cast<int>(WindowPositioner::ConstraintAdjustment::flip_y)) {
+    WindowPoint const result =
+        constrain_to(parent_rect,
+                     anchor_position_for(
+                         anchor_rect, flip_anchor_y(positioner.parent_anchor)) +
+                         flip_offset_y(positioner.offset)) +
+        offset_for(child_size, flip_anchor_y(positioner.child_anchor));
+
+    if (output_rect.contains({result, child_size})) {
+      return WindowRectangle{result, child_size};
+    }
+  }
+
+  if (static_cast<int>(positioner.constraint_adjustment) &
+          static_cast<int>(WindowPositioner::ConstraintAdjustment::flip_x) &&
+      static_cast<int>(positioner.constraint_adjustment) &
+          static_cast<int>(WindowPositioner::ConstraintAdjustment::flip_y)) {
+    WindowPoint const result =
+        constrain_to(
+            parent_rect,
+            anchor_position_for(anchor_rect, flip_anchor_x(flip_anchor_y(
+                                                 positioner.parent_anchor))) +
+                flip_offset_x(flip_offset_y(positioner.offset))) +
+        offset_for(child_size,
+                   flip_anchor_x(flip_anchor_y(positioner.child_anchor)));
+
+    if (output_rect.contains({result, child_size})) {
+      return WindowRectangle{result, child_size};
+    }
+  }
+
+  {
+    WindowPoint result =
+        constrain_to(parent_rect, anchor_position_for(
+                                      anchor_rect, positioner.parent_anchor) +
+                                      positioner.offset) +
+        offset_for(child_size, positioner.child_anchor);
+
+    if (static_cast<int>(positioner.constraint_adjustment) &
+        static_cast<int>(WindowPositioner::ConstraintAdjustment::slide_x)) {
+      int const left_overhang = result.x - output_rect.top_left.x;
+      int const right_overhang =
+          (result.x + child_size.width) -
+          (output_rect.top_left.x + output_rect.size.width);
+
+      if (left_overhang < 0) {
+        result.x -= left_overhang;
+      } else if (right_overhang > 0) {
+        result.x -= right_overhang;
+      }
+    }
+
+    if (static_cast<int>(positioner.constraint_adjustment) &
+        static_cast<int>(WindowPositioner::ConstraintAdjustment::slide_y)) {
+      int const top_overhang = result.y - output_rect.top_left.y;
+      int const bot_overhang =
+          (result.y + child_size.height) -
+          (output_rect.top_left.y + output_rect.size.height);
+
+      if (top_overhang < 0) {
+        result.y -= top_overhang;
+      } else if (bot_overhang > 0) {
+        result.y -= bot_overhang;
+      }
+    }
+
+    if (output_rect.contains({result, child_size})) {
+      return WindowRectangle{result, child_size};
+    }
+  }
+
+  {
+    WindowPoint result =
+        constrain_to(parent_rect, anchor_position_for(
+                                      anchor_rect, positioner.parent_anchor) +
+                                      positioner.offset) +
+        offset_for(child_size, positioner.child_anchor);
+
+    if (static_cast<int>(positioner.constraint_adjustment) &
+        static_cast<int>(WindowPositioner::ConstraintAdjustment::resize_x)) {
+      int const left_overhang = result.x - output_rect.top_left.x;
+      int const right_overhang =
+          (result.x + child_size.width) -
+          (output_rect.top_left.x + output_rect.size.width);
+
+      if (left_overhang < 0) {
+        result.x -= left_overhang;
+        child_size.width += left_overhang;
+      }
+
+      if (right_overhang > 0) {
+        child_size.width -= right_overhang;
+      }
+    }
+
+    if (static_cast<int>(positioner.constraint_adjustment) &
+        static_cast<int>(WindowPositioner::ConstraintAdjustment::resize_y)) {
+      int const top_overhang = result.y - output_rect.top_left.y;
+      int const bot_overhang =
+          (result.y + child_size.height) -
+          (output_rect.top_left.y + output_rect.size.height);
+
+      if (top_overhang < 0) {
+        result.y -= top_overhang;
+        child_size.height += top_overhang;
+      }
+
+      if (bot_overhang > 0) {
+        child_size.height -= bot_overhang;
+      }
+    }
+
+    if (output_rect.contains({result, child_size})) {
+      return WindowRectangle{result, child_size};
+    }
+  }
+
+  return default_result;
+}
+
+}  // namespace flutter