callbacks.h File Reference

GLFW input handling callbacks for neuron visualization. More...

#include <GLFW/glfw3.h>
#include <iostream>
#include <vector>
#include "neurongraph.h"
#include "globals.h"
#include "opgl_utils.h"

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Functions
void	keyCallback (GLFWwindow *window, int key, int scancode, int action, int mods)
	Handles keyboard input events. More...
void	mouseButtonCallback (GLFWwindow *window, int button, int action, int mods)
	Handles mouse button input events. More...
void	cursorPosCallback (GLFWwindow *window, double xpos, double ypos)
	Handles mouse cursor movement. More...
void	scrollCallback (GLFWwindow *window, double xoffset, double yoffset)
	Handles mouse scroll events. More...

Detailed Description

GLFW input handling callbacks for neuron visualization.

This header defines the callback functions that handle user input through GLFW, including keyboard, mouse, and scroll wheel interactions for the neuron viewer. These callbacks modify the global state in globals.h to control the visualization.

Author

CPPNeuronMesher Team

Date

2025-07-27

Version

1.0

Copyright

MIT License

Function Documentation

cursorPosCallback()

void cursorPosCallback	(	GLFWwindow *	window,
		double	xpos,
		double	ypos
	)

Handles mouse cursor movement.

Updates camera orientation or position based on mouse movement when:

• Left button is held: Rotate view
• Right button is held: Pan view
• Middle button is held: Zoom view

Parameters

window	The GLFW window that received the event
xpos	The new cursor x-coordinate, relative to the left edge of the content area
ypos	The new cursor y-coordinate, relative to the top edge of the content area

Handles mouse cursor movement.

Parameters

[in]	window	The GLFW window that received the event
[in]	xpos	The new x-coordinate of the cursor, in screen coordinates
[in]	ypos	The new y-coordinate of the cursor, in screen coordinates

This callback function processes mouse movement to implement interactive 3D view manipulation. It provides the following functionality:

• Left-drag: Rotates the view around the X and Y axes
• Right-drag: Pans the view in the X and Y directions

The function uses the difference between the current and last cursor positions to calculate the amount of rotation or panning to apply. The actual view transformation is applied in the main rendering loop using the global state variables modified by this function.

Note

The function updates the lastX and lastY variables to track cursor movement between frames

Rotation and panning speeds are scaled by constant factors (0.3f and 1.5f)

See also

mouseButtonCallback() for enabling/disabling rotation and panning

GLFW cursor position documentation: https://www.glfw.org/docs/latest/input_guide.html#cursor_pos

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keyCallback()

void keyCallback	(	GLFWwindow *	window,
		int	key,
		int	scancode,
		int	action,
		int	mods
	)

Handles keyboard input events.

Processes key presses and releases to control the visualization:

• WASD: Move camera left/right/forward/backward
• QE: Move camera up/down
• Arrow keys: Rotate view
• R: Reset view
• Space: Toggle auto-rotation
• 1-5: Switch between rendering modes
• +/-: Adjust rendering parameters
• ESC: Close window
• H: Toggle help text

Parameters

window	The GLFW window that received the event
key	The keyboard key that was pressed or released
scancode	The system-specific scancode of the key
action	GLFW_PRESS, GLFW_RELEASE or GLFW_REPEAT
mods	Bit field describing which modifier keys were held down

Handles keyboard input events.

Parameters

[in]	window	The GLFW window that received the event
[in]	key	The keyboard key that was pressed or released
[in]	scancode	The system-specific scancode of the key
[in]	action	The key action (GLFW_PRESS, GLFW_RELEASE, or GLFW_REPEAT)
[in]	mods	Bit field describing which modifier keys were held down

This callback function processes keyboard input for controlling the neuron viewer. It implements the following keyboard shortcuts:

• F: Refine neuron geometry (halve delta)
• Ctrl+F: Coarsen neuron geometry (double delta)
• 1-6: Switch between different render modes
• O: Open a neuron file dialog
• R: Reset camera view
• H: Show/hide help window
• S: Save the current neuron data to file

The function modifies global state for view parameters and triggers updates to the neuron visualization when geometry is refined or coarsened.

Note

The function only processes key press events (GLFW_PRESS)

Modifier keys (Ctrl, Shift, Alt) are checked using the mods parameter

See also

GLFW key documentation: https://www.glfw.org/docs/latest/input_guide.html#input_key

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mouseButtonCallback()

void mouseButtonCallback	(	GLFWwindow *	window,
		int	button,
		int	action,
		int	mods
	)

Handles mouse button input events.

Processes mouse button presses and releases for:

• Left button: Start/end rotation
• Right button: Start/end panning
• Middle button: Start/end zooming

Parameters

window	The GLFW window that received the event
button	The mouse button that was pressed or released
action	GLFW_PRESS or GLFW_RELEASE
mods	Bit field describing which modifier keys were held down

Handles mouse button input events.

Parameters

[in]	window	The GLFW window that received the event
[in]	button	The mouse button that was pressed or released
[in]	action	The button action (GLFW_PRESS or GLFW_RELEASE)
[in]	mods	Bit field describing which modifier keys were held down

This callback function processes mouse button events to enable interactive 3D view manipulation. It tracks the following interactions:

• Left mouse button: Enables view rotation when dragged
• Right mouse button: Enables view panning when dragged

The function updates global state variables (dragging, rightDragging) that are used by cursorPosCallback to implement the actual view transformations.

Note

The function tracks both press and release events for smooth interaction

The cursor position is captured on button press for relative movement

See also

cursorPosCallback() for the implementation of the actual view transformations

GLFW mouse button documentation: https://www.glfw.org/docs/latest/input_guide.html#input_mouse_button

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scrollCallback()

void scrollCallback	(	GLFWwindow *	window,
		double	xoffset,
		double	yoffset
	)

Handles mouse scroll events.

Zooms the view in/out based on vertical scroll input.

Parameters

window	The GLFW window that received the event
xoffset	The scroll offset along the x-axis (unused)
yoffset	The scroll offset along the y-axis (positive = scroll up, negative = scroll down)

Handles mouse scroll events.

Parameters

[in]	window	The GLFW window that received the event
[in]	xoffset	The scroll offset along the x-axis (unused in this implementation)
[in]	yoffset	The scroll offset along the y-axis (positive for scroll up, negative for scroll down)

This callback function processes mouse scroll wheel input to implement smooth zooming of the 3D view. It modifies the global zoom factor based on the vertical scroll amount.

The zoom factor is adjusted using an exponential scale (1.1^yoffset) to provide natural-feeling zoom behavior. The zoom level is clamped between 0.05 and 10.0 to prevent extreme zoom levels that might cause rendering issues or numerical instability.

Note

The xoffset parameter is currently unused but included for future compatibility

Zooming is centered on the current view (no focal point adjustment)

The 1.1 base value provides a good balance between precision and responsiveness

See also

GLFW scroll documentation: https://www.glfw.org/docs/latest/input_guide.html#scrolling

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