Atlas - SDL_uikitpen.m
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1/*
2  Simple DirectMedia Layer
3  Copyright (C) 1997-2026 Sam Lantinga <[email protected]>
4
5  This software is provided 'as-is', without any express or implied
6  warranty.  In no event will the authors be held liable for any damages
7  arising from the use of this software.
8
9  Permission is granted to anyone to use this software for any purpose,
10  including commercial applications, and to alter it and redistribute it
11  freely, subject to the following restrictions:
12
13  1. The origin of this software must not be misrepresented; you must not
14     claim that you wrote the original software. If you use this software
15     in a product, an acknowledgment in the product documentation would be
16     appreciated but is not required.
17  2. Altered source versions must be plainly marked as such, and must not be
18     misrepresented as being the original software.
19  3. This notice may not be removed or altered from any source distribution.
20*/
21#include "SDL_internal.h"
22
23#ifdef SDL_VIDEO_DRIVER_UIKIT
24
25#include "SDL_uikitevents.h"
26#include "SDL_uikitpen.h"
27#include "SDL_uikitwindow.h"
28
29#include "../../events/SDL_pen_c.h"
30
31// Fix build errors when using an older SDK by defining these selectors
32#if !defined(SDL_PLATFORM_TVOS)
33
34@interface UITouch (SDL)
35#if !(__IPHONE_OS_VERSION_MAX_ALLOWED >= 170500)
36@property (nonatomic, readonly) CGFloat rollAngle;
37#endif
38@end
39
40@interface UIHoverGestureRecognizer (SDL)
41#if !(__IPHONE_OS_VERSION_MAX_ALLOWED >= 160100)
42@property (nonatomic, readonly) CGFloat zOffset;
43#endif
44#if !(__IPHONE_OS_VERSION_MAX_ALLOWED >= 160400)
45- (CGFloat) azimuthAngleInView:(UIView *) view;
46
47@property (nonatomic, readonly) CGFloat altitudeAngle;
48#endif
49#if !(__IPHONE_OS_VERSION_MAX_ALLOWED >= 170500)
50@property (nonatomic, readonly) CGFloat rollAngle;
51#endif
52@end
53
54#endif // !SDL_PLATFORM_TVOS
55
56static SDL_PenID apple_pencil_id = 0;
57
58bool UIKit_InitPen(SDL_VideoDevice *_this)
59{
60    return true;
61}
62
63// we only have one Apple Pencil at a time, and it must be paired to the iOS device.
64// We only know about its existence when it first sends an event, so add an single SDL pen
65// device here if we haven't already.
66static SDL_PenID UIKit_AddPenIfNecesary(SDL_Window *window)
67{
68    if (!apple_pencil_id) {
69        SDL_PenInfo info;
70        SDL_zero(info);
71        info.capabilities = SDL_PEN_CAPABILITY_PRESSURE | SDL_PEN_CAPABILITY_XTILT | SDL_PEN_CAPABILITY_YTILT;
72        info.max_tilt = 90.0f;
73        info.num_buttons = 0;
74        info.subtype = SDL_PEN_TYPE_PENCIL;
75        info.device_type = SDL_PEN_DEVICE_TYPE_DIRECT;  // Apple Pencil on iOS is always a direct device; it works on the tablet's screen.
76
77        if (@available(iOS 17.5, *)) {  // need rollAngle method.
78            info.capabilities |= SDL_PEN_CAPABILITY_ROTATION;
79        }
80
81        if (@available(ios 16.1, *)) {  // need zOffset method.
82            info.capabilities |= SDL_PEN_CAPABILITY_DISTANCE;
83        }
84
85        // Apple Pencil and iOS can report when the pencil is being "squeezed" but it's a boolean thing,
86        // so we can't use it for tangential pressure.
87
88        // There's only ever one Apple Pencil at most, so we just pass a non-zero value for the handle.
89        apple_pencil_id = SDL_AddPenDevice(0, "Apple Pencil", window, &info, (void *) (size_t) 0x1, true);
90    }
91
92    return apple_pencil_id;
93}
94
95static void UIKit_HandlePenAxes(SDL_Window *window, NSTimeInterval nstimestamp, float zOffset, const CGPoint *point, float force,
96                                float maximumPossibleForce, float azimuthAngleInView, float altitudeAngle, float rollAngle)
97{
98    const SDL_PenID penId = UIKit_AddPenIfNecesary(window);
99    if (penId) {
100        const Uint64 timestamp = UIKit_GetEventTimestamp(nstimestamp);
101        const float radians_to_degrees = 180.0f / SDL_PI_F;
102
103        // Normalize force to 0.0f ... 1.0f range.
104        const float pressure = force / maximumPossibleForce;
105
106        // azimuthAngleInView is in radians, with 0 being the pen's back end pointing due east on the screen when the
107        // tip is touching the screen, and negative when heading north from there, positive to the south.
108        // So convert to degrees, 0 being due east, etc.
109        const float azimuth_angle = azimuthAngleInView * radians_to_degrees;
110
111        // altitudeAngle is in radians, with 0 being the pen laying flat on (parallel to) the device
112        //  screen and PI/2 being it pointing straight up from (perpendicular to) the device screen.
113        // So convert to degrees, 0 being flat and 90 being straight up.
114        const float altitude_angle = altitudeAngle * radians_to_degrees;
115
116        // the azimuth_angle goes from -180 to 180 (with abs(angle) moving from 180 to 0, left to right), but SDL wants
117        // it from -90 (back facing west) to 90 (back facing east).
118        const float xtilt = (180.0f - SDL_fabsf(azimuth_angle)) - 90.0f;
119
120        // the altitude_angle goes from 0 to 90 regardless of which direction the pen is lifting off the device, but SDL wants
121        // it from -90 (flat facing north) to 90 (flat facing south).
122        const float ytilt = (azimuth_angle < 0.0f) ? -(90.0f - altitude_angle) : (90.0f - altitude_angle);
123
124        // rotation is in radians, and only available on a later iOS.
125        const float rotation = rollAngle * radians_to_degrees;  // !!! FIXME: this might need adjustment, I don't have a pencil that supports it.
126
127        if (force == 0.0f && (SDL_GetPenStatus(penId, NULL, 0) & SDL_PEN_INPUT_DOWN)) {
128            // The first hover as the pen is being released has a stale position, so ignore it
129            return;
130        }
131
132        SDL_SendPenMotion(timestamp, penId, window, point->x, point->y);
133        SDL_SendPenAxis(timestamp, penId, window, SDL_PEN_AXIS_PRESSURE, pressure);
134        SDL_SendPenAxis(timestamp, penId, window, SDL_PEN_AXIS_XTILT, xtilt);
135        SDL_SendPenAxis(timestamp, penId, window, SDL_PEN_AXIS_YTILT, ytilt);
136        SDL_SendPenAxis(timestamp, penId, window, SDL_PEN_AXIS_ROTATION, rotation);
137        SDL_SendPenAxis(timestamp, penId, window, SDL_PEN_AXIS_DISTANCE, zOffset);
138    }
139}
140
141#if !defined(SDL_PLATFORM_TVOS)
142void UIKit_HandlePenHover(SDL_uikitview *view, UIHoverGestureRecognizer *recognizer)
143{
144    float zOffset = 0.0f;
145    if (@available(iOS 16.1, *)) {
146        zOffset = (float) [recognizer zOffset];
147    }
148
149    float azimuthAngleInView = 0.0f;
150    if (@available(iOS 16.4, *)) {
151        azimuthAngleInView = (float) [recognizer azimuthAngleInView:view];
152    }
153
154    float altitudeAngle = 0.0f;
155    if (@available(iOS 16.4, *)) {
156        altitudeAngle = (float) [recognizer altitudeAngle];
157    }
158
159    float rollAngle = 0.0f;
160    if (@available(iOS 17.5, *)) {
161        rollAngle = (float) [recognizer rollAngle];
162    }
163
164    SDL_Window *window = [view getSDLWindow];
165    const CGPoint point = [recognizer locationInView:view];
166
167    // force is zero here; if you're here, you're not touching.
168    // !!! FIXME: no timestamp on these...?
169    UIKit_HandlePenAxes(window, 0, zOffset, &point, 0.0f, 1.0f, azimuthAngleInView, altitudeAngle, rollAngle);
170}
171#endif
172
173static void UIKit_HandlePenAxesFromUITouch(SDL_uikitview *view, UITouch *pencil)
174{
175    float rollAngle = 0.0f;
176#if !defined(SDL_PLATFORM_TVOS)
177    if (@available(iOS 17.5, *)) {
178        rollAngle = (float) [pencil rollAngle];
179    }
180#endif
181
182    SDL_Window *window = [view getSDLWindow];
183    const CGPoint point = [pencil locationInView:view];
184
185    // zOffset is zero here; if you're here, you're touching.
186    UIKit_HandlePenAxes(window, [pencil timestamp], 0.0f, &point, [pencil force], [pencil maximumPossibleForce], [pencil azimuthAngleInView:view], [pencil altitudeAngle], rollAngle);
187}
188
189void UIKit_HandlePenMotion(SDL_uikitview *view, UITouch *pencil)
190{
191    UIKit_HandlePenAxesFromUITouch(view, pencil);
192}
193
194void UIKit_HandlePenPress(SDL_uikitview *view, UITouch *pencil)
195{
196    SDL_Window *window = [view getSDLWindow];
197    const SDL_PenID penId = UIKit_AddPenIfNecesary(window);
198    if (penId) {
199        UIKit_HandlePenAxesFromUITouch(view, pencil);
200        SDL_SendPenTouch(UIKit_GetEventTimestamp([pencil timestamp]), penId, window, false, true);
201    }
202}
203
204void UIKit_HandlePenRelease(SDL_uikitview *view, UITouch *pencil)
205{
206    SDL_Window *window = [view getSDLWindow];
207    const SDL_PenID penId = UIKit_AddPenIfNecesary(window);
208    if (penId) {
209        SDL_SendPenTouch(UIKit_GetEventTimestamp([pencil timestamp]), penId, window, false, false);
210        UIKit_HandlePenAxesFromUITouch(view, pencil);
211    }
212}
213
214void UIKit_QuitPen(SDL_VideoDevice *_this)
215{
216    if (apple_pencil_id) {
217        SDL_RemovePenDevice(0, NULL, apple_pencil_id);
218        apple_pencil_id = 0;
219    }
220}
221
222#endif // SDL_VIDEO_DRIVER_UIKIT
223
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