Add guide documentation & fixes

README.md

@@ -132,7 +132,7 @@ information on what to include when reporting a bug.
  - [Null] Added EGL context creation on Mesa via `EGL_MESA_platform_surfaceless`
  - [EGL] Allowed native access on Wayland with `GLFW_CONTEXT_CREATION_API` set to
    `GLFW_NATIVE_CONTEXT_API` (#2518)
- - [Cocoa] Added `glfwSetTrackpadZoomCallback` and `glfwSetTrackpadRotateCallback`
+ - [Cocoa & Wayland] Added `glfwSetTrackpadZoomCallback` and `glfwSetTrackpadRotateCallback`
    for trackpad zoom and rotate events (#90)
 
 

docs/input.md

@@ -581,6 +581,42 @@ void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
 
 A normal mouse wheel, being vertical, provides offsets along the Y-axis.
 
+### Trackpad zoom and rotate {#input_mouse_trackpad_gestures}
+
+Trackpad events are currently only available on macOS and Wayland (Linux).
+
+If you wish to be notified when a zoom gesture is performed on a trackpad,
+set the trackpadZoom callback.
+
+```c
+glfwSetTrackpadZoomCallback(window, trackpad_zoom_callback);
+```
+
+The callback function receives the scale of the zoom, which is a ratio that
+should be multiplied by the current zoom level to get the new zoom level.
+
+```c
+static void trackpad_zoom_callback(GLFWwindow* window, double scale)
+{
+    my_app->zoom_level *= scale;
+}
+```
+
+For trackpad rotate gestures, set the trackpadRotateCallback.
+
+```c
+glfwSetTrackpadRotateCallback(window, trackpad_rotate_callback);
+```
+
+The callback function recieves the angle, in degrees, to rotate by.
+
+```c
+static void trackpad_rotate_callback(GLFWwindow* window, double angle)
+{
+    my_app->rotation_angle_degrees += angle;
+}
+```
+
 
 ## Joystick input {#joystick}
 

include/GLFW/glfw3.h

@@ -1880,7 +1880,8 @@ typedef void (* GLFWscrollfun)(GLFWwindow* window, double xoffset, double yoffse
  *  @endcode
  *
  *  @param[in] window The window that received the event.
- *  @param[in] scale The manigification amount, as a scale factor
+ *  @param[in] scale The manigification amount, to be multiplied by the current
+ *  scale factor to get the new scale factor.
  *
  *  @sa @ref glfwSetTrackpadZoomCallback
  *

src/input.c

@@ -1069,7 +1069,7 @@ GLFWAPI GLFWtrackpadzoomfun glfwSetTrackpadZoomCallback(GLFWwindow* handle,
     return cbfun;
 }
 
-GLFWAPI GLFWtrackpadzoomfun glfwSetTrackpadRotateCallback(GLFWwindow* handle,
+GLFWAPI GLFWtrackpadrotatefun glfwSetTrackpadRotateCallback(GLFWwindow* handle,
                                                           GLFWtrackpadrotatefun cbfun)
 {
     _GLFWwindow* window = (_GLFWwindow*) handle;