backends: Add helpers to convert from clutter tool button to evcode

This complements the existing clutter->evdev and evdev->clutter helpers,
but this time for buttons we expect from a stylus tool. We also need to
convert left/middle/right for the Wacom puck/lens cursor tools but that
particular conversion is lossy.

Note that these are more restrictive than the normal codes - if we
get "other" buttons from a stylus we don't really know what they could
possibly map to. So we safely map what looks like buttons from a mouse
but otherwise complain and return zero.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3649>

src/backends/meta-backend-private.h

@@ -223,5 +223,11 @@ char * meta_backend_get_vendor_name (MetaBackend *backend,
 META_EXPORT_TEST
 uint32_t meta_clutter_button_to_evdev (uint32_t clutter_button);
 
+META_EXPORT_TEST
+uint32_t meta_clutter_tool_button_to_evdev (uint32_t clutter_button);
+
 META_EXPORT_TEST
 uint32_t meta_evdev_button_to_clutter (uint32_t evdev_button);
+
+META_EXPORT_TEST
+uint32_t meta_evdev_tool_button_to_clutter (uint32_t evdev_button);

src/backends/meta-backend.c

@@ -123,6 +123,11 @@ static guint signals[N_SIGNALS];
 #define BTN_LEFT 0x110
 #define BTN_RIGHT 0x111
 #define BTN_MIDDLE 0x112
+#define BTN_STYLUS3 0x149
+#define BTN_TOUCH 0x14a
+#define BTN_STYLUS 0x14b
+#define BTN_STYLUS2 0x14c
+#define BTN_JOYSTICK 0x120
 #endif
 
 struct _MetaBackendPrivate
@@ -1853,6 +1858,50 @@ meta_clutter_button_to_evdev (uint32_t clutter_button)
   return (clutter_button + (BTN_LEFT - 1)) - 4;
 }
 
+uint32_t
+meta_clutter_tool_button_to_evdev (uint32_t clutter_button)
+{
+  switch (clutter_button)
+    {
+    case CLUTTER_BUTTON_PRIMARY:
+      return BTN_TOUCH;
+    case CLUTTER_BUTTON_MIDDLE:
+      return BTN_STYLUS;
+    case CLUTTER_BUTTON_SECONDARY:
+      return BTN_STYLUS2;
+    case 8:
+      return BTN_STYLUS3;
+    }
+
+  return (clutter_button + (BTN_LEFT - 1)) - 5;
+}
+
+uint32_t
+meta_evdev_tool_button_to_clutter (uint32_t evdev_button)
+{
+  switch (evdev_button)
+    {
+    case BTN_TOUCH:
+    case BTN_LEFT:
+      return CLUTTER_BUTTON_PRIMARY;
+    case BTN_STYLUS:
+    case BTN_MIDDLE:
+      return CLUTTER_BUTTON_MIDDLE;
+    case BTN_STYLUS2:
+    case BTN_RIGHT:
+      return CLUTTER_BUTTON_SECONDARY;
+    case BTN_STYLUS3:
+      return 8;
+    }
+
+  g_return_val_if_fail (evdev_button > BTN_LEFT, 0);
+  g_return_val_if_fail (evdev_button < BTN_JOYSTICK, 0);
+
+  /* For compatibility reasons, all additional buttons (i.e. BTN_SIDE and
+   * higher) go after the old 4-7 scroll ones and 8 for BTN_STYLUS3 */
+  return (evdev_button - (BTN_LEFT - 1)) + 5;
+}
+
 uint32_t
 meta_evdev_button_to_clutter (uint32_t evdev_button)
 {

src/tests/button-transform-tests.c

@@ -106,6 +106,97 @@ meta_test_evdev_to_clutter_to_evdev (void)
     }
 }
 
+static void
+meta_test_evdev_tool_to_clutter (void)
+{
+  struct {
+    uint32_t evdev_button;
+    uint32_t clutter_button;
+  } test_cases[] = {
+    { .evdev_button = BTN_TOUCH, .clutter_button = CLUTTER_BUTTON_PRIMARY },
+    { .evdev_button = BTN_STYLUS, .clutter_button = CLUTTER_BUTTON_MIDDLE },
+    { .evdev_button = BTN_STYLUS2, .clutter_button = CLUTTER_BUTTON_SECONDARY },
+    { .evdev_button = BTN_STYLUS3, .clutter_button = 8 },
+    { .evdev_button = BTN_LEFT, .clutter_button = CLUTTER_BUTTON_PRIMARY },
+    { .evdev_button = BTN_MIDDLE, .clutter_button = CLUTTER_BUTTON_MIDDLE },
+    { .evdev_button = BTN_RIGHT, .clutter_button = CLUTTER_BUTTON_SECONDARY },
+    /* fallback behavior */
+    { .evdev_button = BTN_SIDE, .clutter_button = 9 },
+    { .evdev_button = BTN_EXTRA, .clutter_button = 10 },
+  };
+  size_t i;
+
+  for (i = 0; i < G_N_ELEMENTS (test_cases); i++)
+    {
+      uint32_t evdev_button;
+      uint32_t expected_clutter_button;
+      uint32_t clutter_button;
+
+      evdev_button = test_cases[i].evdev_button;
+      expected_clutter_button = test_cases[i].clutter_button;
+
+      clutter_button = meta_evdev_tool_button_to_clutter (evdev_button);
+      g_assert_cmpuint (clutter_button, ==, expected_clutter_button);
+    }
+}
+
+static void
+meta_test_clutter_tool_to_evdev (void)
+{
+  struct {
+    uint32_t clutter_button;
+    uint32_t evdev_button;
+  } test_cases[] = {
+    { .clutter_button = CLUTTER_BUTTON_PRIMARY, .evdev_button = BTN_TOUCH },
+    { .clutter_button = CLUTTER_BUTTON_MIDDLE, .evdev_button = BTN_STYLUS },
+    { .clutter_button = CLUTTER_BUTTON_SECONDARY, .evdev_button = BTN_STYLUS2 },
+    { .clutter_button = 8, .evdev_button = BTN_STYLUS3 },
+    /* fallback behavior */
+    { .clutter_button = 9, .evdev_button = BTN_SIDE },
+    { .clutter_button = 10, .evdev_button = BTN_EXTRA },
+  };
+  size_t i;
+
+  for (i = 0; i < G_N_ELEMENTS (test_cases); i++)
+    {
+      uint32_t clutter_button;
+      uint32_t expected_evdev_button;
+      uint32_t evdev_button;
+
+      clutter_button = test_cases[i].clutter_button;
+      expected_evdev_button = test_cases[i].evdev_button;
+
+      evdev_button = meta_clutter_tool_button_to_evdev (clutter_button);
+      g_assert_cmpuint (evdev_button, ==, expected_evdev_button);
+    }
+}
+
+static void
+meta_test_evdev_tool_to_clutter_tool_to_evdev (void)
+{
+  uint32_t test_cases[] = {
+    BTN_TOUCH,
+    BTN_STYLUS,
+    BTN_STYLUS2,
+    BTN_STYLUS3,
+  };
+  size_t i;
+
+  for (i = 0; i < G_N_ELEMENTS (test_cases); i++)
+    {
+      uint32_t evdev_button;
+      uint32_t expected_evdev_button;
+      uint32_t clutter_button;
+
+      evdev_button = test_cases[i];
+      expected_evdev_button = evdev_button;
+
+      clutter_button = meta_evdev_tool_button_to_clutter (evdev_button);
+      evdev_button = meta_clutter_tool_button_to_evdev (clutter_button);
+      g_assert_cmpuint (evdev_button, ==, expected_evdev_button);
+    }
+}
+
 void
 init_button_transform_tests (void)
 {
@@ -115,4 +206,10 @@ init_button_transform_tests (void)
                    meta_test_evdev_to_clutter);
   g_test_add_func ("/backends/button-transform/evdev-clutter-evdev",
                    meta_test_evdev_to_clutter_to_evdev);
+  g_test_add_func ("/backends/button-transform/evdev-tool-clutter",
+                   meta_test_evdev_tool_to_clutter);
+  g_test_add_func ("/backends/button-transform/clutter-tool-to-evdev",
+                   meta_test_clutter_tool_to_evdev);
+  g_test_add_func ("/backends/button-transform/evdev-tool-clutter-tool-evdev",
+                   meta_test_evdev_tool_to_clutter_tool_to_evdev);
 }