Mercurial > minori

comparison dep/animone/src/a11y/win32.cc @ 340:74e2365326c6

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
dep/animone: add experimental accessibility strategy I also moved most of the functions out of util/win32.cc, because that file is meant for things that are shared between the different functions, and currently that is only wide string conversion helpers.
author Paper <paper@paper.us.eu.org>
date Wed, 19 Jun 2024 23:13:55 -0400
parents
children 052ec053ee37
comparison
equal deleted inserted replaced
339:eac06513db86 340:74e2365326c6
1 #include <functional>
2 #include <string>
3 #include <vector>
4
5 #include <windows.h>
6 #include <uiautomation.h>
7
8 #include "animone/a11y.h"
9 #include "animone/a11y/win32.h"
10
11 namespace animone::internal::win32 {
12
13 // Windows Accessibility API reference:
14 // https://msdn.microsoft.com/en-us/library/windows/desktop/ff486375.aspx
15
16 // Commonly used interfaces
17 using Element = IUIAutomationElement;
18 using TreeWalker = IUIAutomationTreeWalker;
19 using ValuePattern = IUIAutomationValuePattern;
20
21 using element_proc_t = std::function<TreeScope(Element&)>;
22 using properties_t = std::vector<std::pair<long, bool>>;
23
24 // The main interface that is used throughout this file. Must be initialized
25 // before it can be used for the first time.
26 static ComInterface<IUIAutomation> ui_automation;
27
28 ////////////////////////////////////////////////////////////////////////////////
29
30 static bool InitializeUIAutomation() {
31 if (ui_automation)
32 return true;
33
34 // COM library must be initialized on the current thread before calling
35 // CoCreateInstance.
36 ::CoInitialize(nullptr);
37
38 IUIAutomation* ui_automation_interface = nullptr;
39 const auto result = ::CoCreateInstance(
40 CLSID_CUIAutomation, nullptr, CLSCTX_INPROC_SERVER, IID_IUIAutomation,
41 reinterpret_cast<void**>(&ui_automation_interface));
42 ui_automation.reset(ui_automation_interface);
43
44 return SUCCEEDED(result);
45 }
46
47 ////////////////////////////////////////////////////////////////////////////////
48
49 static Element* GetElementFromHandle(HWND hwnd) {
50 Element* element = nullptr;
51 ui_automation->ElementFromHandle(static_cast<UIA_HWND>(hwnd), &element);
52 return element;
53 }
54
55 static std::wstring GetElementName(Element& element) {
56 std::wstring element_name;
57
58 BSTR bstr = nullptr;
59 if (SUCCEEDED(element.get_CurrentName(&bstr)) && bstr) {
60 element_name = bstr;
61 ::SysFreeString(bstr);
62 }
63
64 return element_name;
65 }
66
67 static std::wstring GetElementValue(Element& element) {
68 std::wstring element_value;
69
70 ValuePattern* value_pattern_interface = nullptr;
71 element.GetCurrentPatternAs(
72 UIA_ValuePatternId, IID_PPV_ARGS(&value_pattern_interface));
73 ComInterface<ValuePattern> value_pattern(value_pattern_interface);
74
75 if (value_pattern) {
76 BSTR bstr = nullptr;
77 if (SUCCEEDED(value_pattern->get_CurrentValue(&bstr)) && bstr) {
78 element_value = bstr;
79 ::SysFreeString(bstr);
80 }
81 }
82
83 return element_value;
84 }
85
86 ////////////////////////////////////////////////////////////////////////////////
87
88 static bool VerifyElementProperties(Element& element, const properties_t& properties) {
89 VARIANT v = {};
90 for (const auto& pair : properties) {
91 if (FAILED(element.GetCurrentPropertyValue(pair.first, &v)))
92 return false;
93 if (v.boolVal != (pair.second ? VARIANT_TRUE : VARIANT_FALSE))
94 return false;
95 }
96
97 return true;
98 }
99
100 static bool IsAddressBarElement(Element& element) {
101 static const properties_t properties = {
102 {UIA_IsEnabledPropertyId, true},
103 {UIA_IsKeyboardFocusablePropertyId, true},
104 {UIA_IsValuePatternAvailablePropertyId, true},
105 {UIA_ValueIsReadOnlyPropertyId, false},
106 };
107
108 return VerifyElementProperties(element, properties);
109 }
110
111 static bool IsTabsElement(Element& element) {
112 static const properties_t properties = {
113 {UIA_ValueIsReadOnlyPropertyId, true},
114 };
115
116 return VerifyElementProperties(element, properties);
117 }
118
119 ////////////////////////////////////////////////////////////////////////////////
120
121 static void WalkElements(TreeWalker& tree_walker, Element& parent, TreeScope scope,
122 size_t depth, element_proc_t element_proc) {
123 constexpr size_t kMaxTreeDepth = 16; // arbitrary value
124 if (depth > kMaxTreeDepth)
125 return;
126
127 if (scope & TreeScope_Element)
128 scope = element_proc(parent);
129
130 auto descend = [](TreeScope scope) {
131 return (scope & TreeScope_Children) || (scope & TreeScope_Descendants);
132 };
133
134 if (descend(scope)) {
135 Element* first_element = nullptr;
136 tree_walker.GetFirstChildElement(&parent, &first_element);
137 ComInterface<Element> element(first_element);
138
139 while (element) {
140 scope = element_proc(*element);
141
142 if (descend(scope))
143 WalkElements(tree_walker, *element, scope, depth + 1, element_proc);
144
145 Element* next_element = nullptr;
146 tree_walker.GetNextSiblingElement(element.get(), &next_element);
147 element.reset(next_element);
148 }
149 }
150 }
151
152 static bool FindWebBrowserElements(Element& parent, std::wstring& address,
153 std::vector<std::wstring>& tabs) {
154 TreeWalker* tree_walker_interface = nullptr;
155 ui_automation->get_ControlViewWalker(&tree_walker_interface);
156 ComInterface<TreeWalker> tree_walker(tree_walker_interface);
157
158 if (!tree_walker)
159 return false;
160
161 auto element_proc = [&](Element& element) -> TreeScope {
162 CONTROLTYPEID control_type_id = 0;
163 element.get_CurrentControlType(&control_type_id);
164
165 switch (control_type_id) {
166 default:
167 // Are we done?
168 if (!address.empty() && !tabs.empty())
169 return TreeScope_Element;
170 // Otherwise continue descending the tree.
171 return TreeScope_Descendants;
172
173 case UIA_DocumentControlTypeId:
174 case UIA_MenuBarControlTypeId:
175 case UIA_TitleBarControlTypeId:
176 // We do not need to walk through these nodes. In fact, skipping
177 // documents dramatically improves our performance on worst case
178 // scenarios. This is the whole reason we are walking the tree rather
179 // than using FindFirst and FindAll methods.
180 return TreeScope_Element;
181
182 case UIA_EditControlTypeId:
183 // Here we assume that the first edit control that fits our properties
184 // is the address bar (e.g. "Omnibox" on Chrome, "Awesome Bar" on
185 // Firefox). This element is named differently on each web browser
186 // (e.g. "Address and search bar" on Chrome, "Search or enter address"
187 // on Firefox). This name can change depending on the browser
188 // language. However, we are only interested in the element value,
189 // which usually gives us the URL of the current page.
190 if (address.empty() && IsAddressBarElement(element)) {
191 address = GetElementValue(element);
192 return TreeScope_Element;
193 } else {
194 // Opera has an edit control ("Address field") within another edit
195 // control ("Address bar").
196 return TreeScope_Descendants;
197 }
198
199 case UIA_TabControlTypeId:
200 if (tabs.empty() && IsTabsElement(element))
201 return TreeScope_Children;
202 return TreeScope_Element;
203
204 case UIA_TabItemControlTypeId:
205 tabs.push_back(GetElementName(element));
206 return TreeScope_Element;
207 }
208 };
209
210 WalkElements(*tree_walker, parent, TreeScope_Subtree, 0, element_proc);
211 return true;
212 }
213
214 /* ------------------------------------------------------------------------------------ */
215
216 bool GetWebBrowserInformation(const Window& window, web_browser_proc_t web_browser_proc) {
217 if (!web_browser_proc)
218 return false;
219
220 if (!InitializeUIAutomation())
221 return false;
222
223 ComInterface<Element> parent(GetElementFromHandle(hwnd));
224 if (!parent)
225 return false;
226
227 const std::string title = ToUtf8String(GetElementName(*parent));
228 web_browser_proc({WebBrowserInformationType::Title, title});
229
230 std::wstring address;
231 std::vector<std::wstring> tabs;
232
233 if (!FindWebBrowserElements(*parent, address, tabs))
234 return false;
235
236 web_browser_proc({WebBrowserInformationType::Address, ToUtf8String(address)});
237 for (const auto& tab : tabs)
238 web_browser_proc({WebBrowserInformationType::Tab, ToUtf8String(tab)});
239
240 return true;
241 }
242
243 } // namespace animone::internal::win32