Demo input event transformations with AccessibilityManager

canonical · Feb 11, 2025 · f503e0e · f503e0e
1 parent 39f125e
commit f503e0e
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Showing 4 changed files with 89 additions and 2 deletions.
diff --git a/src/include/server/mir/shell/accessibility_manager.h b/src/include/server/mir/shell/accessibility_manager.h
@@ -17,6 +17,7 @@
 #ifndef MIR_SHELL_ACCESSIBILITY_MANAGER_H
 #define MIR_SHELL_ACCESSIBILITY_MANAGER_H
 
+#include "mir/input/input_event_transformer.h"
 #include <memory>
 #include <optional>
 #include <vector>
@@ -29,6 +30,8 @@ class KeyboardHelper;
 class AccessibilityManager
 {
 public:
+    AccessibilityManager(std::shared_ptr<input::InputEventTransformer> const& event_transformer);
+
     void register_keyboard_helper(std::shared_ptr<shell::KeyboardHelper> const&);
 
     std::optional<int> repeat_rate() const;
@@ -47,6 +50,9 @@ class AccessibilityManager
     int repeat_rate_{25};
     int repeat_delay_{600};
     bool enable_key_repeat{true};
+
+    std::shared_ptr<mir::input::InputEventTransformer> const event_transformer;
+    std::shared_ptr<mir::input::InputEventTransformer::Transformer> const transformer;
 };
 }
 }

diff --git a/src/server/shell/accessibility_manager.cpp b/src/server/shell/accessibility_manager.cpp
@@ -14,10 +14,25 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "mir/input/input_event_transformer.h"
+
+#include "mir/geometry/displacement.h"
 #include "mir/shell/accessibility_manager.h"
+#include "mir/events/scroll_axis.h"
+#include "mir/log.h"
 #include "mir/shell/keyboard_helper.h"
+#include "mir_toolkit/events/enums.h"
+#include "mir_toolkit/events/event.h"
+#include "mir_toolkit/events/input/input_event.h"
+#include "mir_toolkit/events/input/keyboard_event.h"
+#include "mircommon/mir/event_printer.h"
+
+#include <xkbcommon/xkbcommon-keysyms.h>
 
+#include <memory>
 #include <optional>
+#include <sstream>
+
 
 void mir::shell::AccessibilityManager::register_keyboard_helper(std::shared_ptr<KeyboardHelper> const& helper)
 {
@@ -51,3 +66,68 @@ void mir::shell::AccessibilityManager::notify_helpers() const {
     for(auto const& helper: keyboard_helpers)
         helper->repeat_info_changed(repeat_rate(), repeat_delay());
 }
+
+struct MouseKeysTransformer: public mir::input::InputEventTransformer::Transformer
+{
+    std::optional<mir::EventUPtr> transform_input_event(mir::input::EventBuilder* builder, MirEvent const& event) override
+    {
+        using namespace mir; // For operator<<
+
+        std::stringstream ss;
+        ss << const_cast<MirEvent&>(event);
+        mir::log_debug("%s", ss.str().c_str());
+
+        if (mir_event_get_type(&event) != mir_event_type_input)
+            return std::nullopt;
+
+        MirInputEvent const* input_event = mir_event_get_input_event(&event);
+
+        if (mir_input_event_get_type(input_event) == mir_input_event_type_key)
+        {
+            MirKeyboardEvent const* kev = mir_input_event_get_keyboard_event(input_event);
+            if (mir_keyboard_event_action(kev) != mir_keyboard_action_down &&
+                mir_keyboard_event_action(kev) != mir_keyboard_action_repeat)
+                return std::nullopt;
+
+            auto offset = geometry::DisplacementF{};
+            switch (mir_keyboard_event_keysym(kev))
+            {
+            case XKB_KEY_KP_2:
+                offset = geometry::DisplacementF{0, 10};
+                break;
+            case XKB_KEY_KP_4:
+                offset = geometry::DisplacementF{-10, 0};
+                break;
+            case XKB_KEY_KP_6:
+                offset = geometry::DisplacementF{10, 0};
+                break;
+            case XKB_KEY_KP_8:
+                offset = geometry::DisplacementF{0, -10};
+                break;
+
+            default:
+                return std::nullopt;
+            }
+
+            return builder->pointer_event(
+                std::nullopt,
+                mir_pointer_action_motion,
+                0,
+                std::nullopt,
+                offset,
+                mir_pointer_axis_source_none,
+                mir::events::ScrollAxisH{},
+                mir::events::ScrollAxisV{});
+        }
+
+        return std::nullopt;
+    }
+};
+
+mir::shell::AccessibilityManager::AccessibilityManager(
+    std::shared_ptr<input::InputEventTransformer> const& event_transformer) :
+    event_transformer{event_transformer},
+    transformer{std::make_shared<MouseKeysTransformer>()}
+{
+    event_transformer->append(transformer);
+}
diff --git a/src/server/shell/default_configuration.cpp b/src/server/shell/default_configuration.cpp
@@ -188,9 +188,9 @@ mir::DefaultServerConfiguration::the_shell_display_layout()
 auto mir::DefaultServerConfiguration::the_accessibility_manager() -> std::shared_ptr<shell::AccessibilityManager>
 {
     return accessibility_manager(
-        []
+        [this]
         {
-            return std::make_shared<shell::AccessibilityManager>();
+            return std::make_shared<shell::AccessibilityManager>(the_input_event_transformer());
         });
 }
 
diff --git a/src/server/symbols.map b/src/server/symbols.map
@@ -1426,6 +1426,7 @@ global:
     mir::input::InputEventTransformer::append*;
     mir::input::InputEventTransformer::handle*;
     mir::shell::AbstractShell::is_above*;
+    mir::shell::AccessibilityManager::AccessibilityManager*;
     mir::shell::ShellWrapper::is_above*;
     mir::shell::SurfaceStackWrapper::is_above*;
     mir::shell::TokenAuthority::Token::operator*;