1 /***************************************************************************
2  * Copyright (c) 2024 Microsoft Corporation
3  *
4  * This program and the accompanying materials are made available under the
5  * terms of the MIT License which is available at
6  * https://opensource.org/licenses/MIT.
7  *
8  * SPDX-License-Identifier: MIT
9  **************************************************************************/
10 
11 
12 /**************************************************************************/
13 /**************************************************************************/
14 /**                                                                       */
15 /** GUIX Component                                                        */
16 /**                                                                       */
17 /**   Scrollbar Management (Scrollbar)                                    */
18 /**                                                                       */
19 /**************************************************************************/
20 
21 #define GX_SOURCE_CODE
22 
23 /* Include necessary system files.  */
24 
25 #include "gx_api.h"
26 #include "gx_system.h"
27 #include "gx_display.h"
28 #include "gx_context.h"
29 #include "gx_widget.h"
30 #include "gx_utility.h"
31 #include "gx_scrollbar.h"
32 
33 /**************************************************************************/
34 /*                                                                        */
35 /*  FUNCTION                                               RELEASE        */
36 /*                                                                        */
37 /*    _gx_scrollbar_thumb_shift_limit                     PORTABLE C      */
38 /*                                                           6.1          */
39 /*  AUTHOR                                                                */
40 /*                                                                        */
41 /*    Kenneth Maxwell, Microsoft Corporation                              */
42 /*                                                                        */
43 /*  DESCRIPTION                                                           */
44 /*                                                                        */
45 /*    Limit the travel of a scrollbar thumb button so that it cannot      */
46 /*    shift outside parent's limits.                                      */
47 /*                                                                        */
48 /*  INPUT                                                                 */
49 /*                                                                        */
50 /*    thumb                                 Thumb button control block    */
51 /*    shift                                 Requested shift amount        */
52 /*                                                                        */
53 /*  OUTPUT                                                                */
54 /*                                                                        */
55 /*    Shift                                 Allowed shift amount          */
56 /*                                                                        */
57 /*  CALLS                                                                 */
58 /*                                                                        */
59 /*    None                                                                */
60 /*                                                                        */
61 /*  CALLED BY                                                             */
62 /*                                                                        */
63 /*    Application Code                                                    */
64 /*    GUIX Internal Code                                                  */
65 /*                                                                        */
66 /*  RELEASE HISTORY                                                       */
67 /*                                                                        */
68 /*    DATE              NAME                      DESCRIPTION             */
69 /*                                                                        */
70 /*  05-19-2020     Kenneth Maxwell          Initial Version 6.0           */
71 /*  09-30-2020     Kenneth Maxwell          Modified comment(s),          */
72 /*                                            resulting in version 6.1    */
73 /*                                                                        */
74 /**************************************************************************/
_gx_scroll_thumb_shift_limit(GX_SCROLL_THUMB * thumb,INT shift)75 INT _gx_scroll_thumb_shift_limit(GX_SCROLL_THUMB *thumb, INT shift)
76 {
77 INT           minlimit;
78 INT           maxlimit;
79 INT           shiftpos;
80 GX_WIDGET    *parent;
81 GX_SCROLLBAR *bar;
82 GX_RECTANGLE  parentsize;
83 ULONG         style;
84 
85     /* pick up thumb style */
86     style = thumb -> gx_widget_style;
87 
88     /* pick up parent scrollbar */
89     parent = thumb -> gx_widget_parent;
90     parentsize = parent -> gx_widget_size;
91 
92     bar = (GX_SCROLLBAR *)parent;
93 
94     if (style & GX_SCROLLBAR_VERTICAL)
95     {
96         minlimit = parentsize.gx_rectangle_top + bar -> gx_scrollbar_appearance.gx_scroll_thumb_travel_min;
97         maxlimit = parentsize.gx_rectangle_bottom - bar -> gx_scrollbar_appearance.gx_scroll_thumb_travel_max;
98 
99         if (shift > 0)
100         {
101             /* shifting down, don't allow down too far */
102             shiftpos = thumb -> gx_widget_size.gx_rectangle_bottom + shift;
103             if (shiftpos > maxlimit)
104             {
105                 shift = maxlimit - thumb -> gx_widget_size.gx_rectangle_bottom;
106             }
107         }
108         else
109         {
110             /* shifting up, don't allow shift up too far */
111             shiftpos = thumb -> gx_widget_size.gx_rectangle_top + shift;
112             if (shiftpos < minlimit)
113             {
114                 shift = minlimit - thumb -> gx_widget_size.gx_rectangle_top;
115             }
116         }
117     }
118     else
119     {
120         minlimit = parentsize.gx_rectangle_left + bar -> gx_scrollbar_appearance.gx_scroll_thumb_travel_min;
121         maxlimit = parentsize.gx_rectangle_right - bar -> gx_scrollbar_appearance.gx_scroll_thumb_travel_max;
122 
123         if (shift > 0)
124         {
125             /* shifting right, don't allow down too over */
126             shiftpos = thumb -> gx_widget_size.gx_rectangle_right + shift;
127             if (shiftpos > maxlimit)
128             {
129                 shift = maxlimit - thumb -> gx_widget_size.gx_rectangle_right;
130             }
131         }
132         else
133         {
134             /* shifting left, don't allow shift up too far */
135             shiftpos = thumb -> gx_widget_size.gx_rectangle_left + shift;
136             if (shiftpos < minlimit)
137             {
138                 shift = minlimit - thumb -> gx_widget_size.gx_rectangle_left;
139             }
140         }
141     }
142     return shift;
143 }
144 
145