gui.h

#pragma once

#include "../plugin.h"

/// @page GUI
///
/// This extension defines how the plugin will present its GUI.
///
/// There are two approaches:
/// 1. the plugin creates a window and embeds it into the host's window
/// 2. the plugin creates a floating window
///
/// Embedding the window gives more control to the host, and feels more integrated.
/// Floating window are sometimes the only option due to technical limitations.
///
/// Showing the GUI works as follow:
///  1. clap_plugin_gui->is_api_supported(), check what can work
///  2. clap_plugin_gui->create(), allocates gui resources
///  3. if the plugin window is floating
///  4.    -> clap_plugin_gui->set_transient()
///  5.    -> clap_plugin_gui->suggest_title()
///  6. else
///  7.    -> clap_plugin_gui->set_scale()
///  8.    -> clap_plugin_gui->can_resize()
///  9.    -> if resizable and has known size from previous session, clap_plugin_gui->set_size()
/// 10.    -> else clap_plugin_gui->get_size(), gets initial size
/// 11.    -> clap_plugin_gui->set_parent()
/// 12. clap_plugin_gui->show()
/// 13. clap_plugin_gui->hide()/show() ...
/// 14. clap_plugin_gui->destroy() when done with the gui
///
/// Resizing the window (initiated by the plugin, if embedded):
/// 1. Plugins calls clap_host_gui->request_resize()
/// 2. If the host returns true the new size is accepted,
///    the host doesn't have to call clap_plugin_gui->set_size().
///    If the host returns false, the new size is rejected.
///
/// Resizing the window (drag, if embedded)):
/// 1. Only possible if clap_plugin_gui->can_resize() returns true
/// 2. Mouse drag -> new_size
/// 3. clap_plugin_gui->adjust_size(new_size) -> working_size
/// 4. clap_plugin_gui->set_size(working_size)

static CLAP_CONSTEXPR const char CLAP_EXT_GUI[] = "clap.gui";

// If your windowing API is not listed here, please open an issue and we'll figure it out.
// https://github.com/free-audio/clap/issues/new

// uses physical size
// embed using https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setparent
static const CLAP_CONSTEXPR char CLAP_WINDOW_API_WIN32[] = "win32";

// uses logical size, don't call clap_plugin_gui->set_scale()
static const CLAP_CONSTEXPR char CLAP_WINDOW_API_COCOA[] = "cocoa";

// uses physical size
// embed using https://specifications.freedesktop.org/xembed-spec/xembed-spec-latest.html
static const CLAP_CONSTEXPR char CLAP_WINDOW_API_X11[] = "x11";

// uses physical size
// embed is currently not supported, use floating windows
static const CLAP_CONSTEXPR char CLAP_WINDOW_API_WAYLAND[] = "wayland";

#ifdef __cplusplus
extern "C" {
#endif

typedef void         *clap_hwnd;
typedef void         *clap_nsview;
typedef unsigned long clap_xwnd;

// Represent a window reference.
typedef struct clap_window {
   const char *api; // one of CLAP_WINDOW_API_XXX
   union {
      clap_nsview cocoa;
      clap_xwnd   x11;
      clap_hwnd   win32;
      void       *ptr; // for anything defined outside of clap
   };
} clap_window_t;

// Information to improve window resizing when initiated by the host or window manager.
typedef struct clap_gui_resize_hints {
   bool can_resize_horizontally;
   bool can_resize_vertically;

   // only if can resize horizontally and vertically
   bool     preserve_aspect_ratio;
   uint32_t aspect_ratio_width;
   uint32_t aspect_ratio_height;
} clap_gui_resize_hints_t;

// Size (width, height) is in pixels; the corresponding windowing system extension is
// responsible for defining if it is physical pixels or logical pixels.
typedef struct clap_plugin_gui {
   // Returns true if the requested gui api is supported
   // [main-thread]
   bool(CLAP_ABI *is_api_supported)(const clap_plugin_t *plugin, const char *api, bool is_floating);

   // Returns true if the plugin has a preferred api.
   // The host has no obligation to honor the plugin preference, this is just a hint.
   // The const char **api variable should be explicitly assigned as a pointer to
   // one of the CLAP_WINDOW_API_ constants defined above, not strcopied.
   // [main-thread]
   bool(CLAP_ABI *get_preferred_api)(const clap_plugin_t *plugin,
                                     const char         **api,
                                     bool                *is_floating);

   // Create and allocate all resources necessary for the gui.
   //
   // If is_floating is true, then the window will not be managed by the host. The plugin
   // can set its window to stays above the parent window, see set_transient().
   // api may be null or blank for floating window.
   //
   // If is_floating is false, then the plugin has to embed its window into the parent window, see
   // set_parent().
   //
   // After this call, the GUI may not be visible yet; don't forget to call show().
   //
   // Returns true if the GUI is successfully created.
   // [main-thread]
   bool(CLAP_ABI *create)(const clap_plugin_t *plugin, const char *api, bool is_floating);

   // Free all resources associated with the gui.
   // [main-thread]
   void(CLAP_ABI *destroy)(const clap_plugin_t *plugin);

   // Set the absolute GUI scaling factor, and override any OS info.
   // Should not be used if the windowing api relies upon logical pixels.
   //
   // If the plugin prefers to work out the scaling factor itself by querying the OS directly,
   // then ignore the call.
   //
   // scale = 2 means 200% scaling.
   //
   // Returns true if the scaling could be applied
   // Returns false if the call was ignored, or the scaling could not be applied.
   // [main-thread]
   bool(CLAP_ABI *set_scale)(const clap_plugin_t *plugin, double scale);

   // Get the current size of the plugin UI.
   // clap_plugin_gui->create() must have been called prior to asking the size.
   //
   // Returns true if the plugin could get the size.
   // [main-thread]
   bool(CLAP_ABI *get_size)(const clap_plugin_t *plugin, uint32_t *width, uint32_t *height);

   // Returns true if the window is resizeable (mouse drag).
   // [main-thread & !floating]
   bool(CLAP_ABI *can_resize)(const clap_plugin_t *plugin);

   // Returns true if the plugin can provide hints on how to resize the window.
   // [main-thread & !floating]
   bool(CLAP_ABI *get_resize_hints)(const clap_plugin_t *plugin, clap_gui_resize_hints_t *hints);

   // If the plugin gui is resizable, then the plugin will calculate the closest
   // usable size which fits in the given size.
   // This method does not change the size.
   //
   // Returns true if the plugin could adjust the given size.
   // [main-thread & !floating]
   bool(CLAP_ABI *adjust_size)(const clap_plugin_t *plugin, uint32_t *width, uint32_t *height);

   // Sets the window size.
   //
   // Returns true if the plugin could resize its window to the given size.
   // [main-thread & !floating]
   bool(CLAP_ABI *set_size)(const clap_plugin_t *plugin, uint32_t width, uint32_t height);

   // Embeds the plugin window into the given window.
   //
   // Returns true on success.
   // [main-thread & !floating]
   bool(CLAP_ABI *set_parent)(const clap_plugin_t *plugin, const clap_window_t *window);

   // Set the plugin floating window to stay above the given window.
   //
   // Returns true on success.
   // [main-thread & floating]
   bool(CLAP_ABI *set_transient)(const clap_plugin_t *plugin, const clap_window_t *window);

   // Suggests a window title. Only for floating windows.
   //
   // [main-thread & floating]
   void(CLAP_ABI *suggest_title)(const clap_plugin_t *plugin, const char *title);

   // Show the window.
   //
   // Returns true on success.
   // [main-thread]
   bool(CLAP_ABI *show)(const clap_plugin_t *plugin);

   // Hide the window, this method does not free the resources, it just hides
   // the window content. Yet it may be a good idea to stop painting timers.
   //
   // Returns true on success.
   // [main-thread]
   bool(CLAP_ABI *hide)(const clap_plugin_t *plugin);
} clap_plugin_gui_t;

typedef struct clap_host_gui {
   // The host should call get_resize_hints() again.
   // [thread-safe & !floating]
   void(CLAP_ABI *resize_hints_changed)(const clap_host_t *host);

   // Request the host to resize the client area to width, height.
   // Return true if the new size is accepted, false otherwise.
   // The host doesn't have to call set_size().
   //
   // Note: if not called from the main thread, then a return value simply means that the host
   // acknowledged the request and will process it asynchronously. If the request then can't be
   // satisfied then the host will call set_size() to revert the operation.
   // [thread-safe & !floating]
   bool(CLAP_ABI *request_resize)(const clap_host_t *host, uint32_t width, uint32_t height);

   // Request the host to show the plugin gui.
   // Return true on success, false otherwise.
   // [thread-safe]
   bool(CLAP_ABI *request_show)(const clap_host_t *host);

   // Request the host to hide the plugin gui.
   // Return true on success, false otherwise.
   // [thread-safe]
   bool(CLAP_ABI *request_hide)(const clap_host_t *host);

   // The floating window has been closed, or the connection to the gui has been lost.
   //
   // If was_destroyed is true, then the host must call clap_plugin_gui->destroy() to acknowledge
   // the gui destruction.
   // [thread-safe]
   void(CLAP_ABI *closed)(const clap_host_t *host, bool was_destroyed);
} clap_host_gui_t;

#ifdef __cplusplus
}
#endif