How Chrome Accessibility Works, Part 2

Follow-up to: http://crrev.com/c/3094450 This section covers the multi-process browser details and introduces many of the specific classes and data structures used for Chrome accessibility. Bug: None Change-Id: I7d53929a87439d7c921f372e0aade4afd9791a7b AX-Relnotes: N/A Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3108459 Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org> Reviewed-by: David Tseng <dtseng@chromium.org> Reviewed-by: Kevin Babbitt <kbabbitt@microsoft.com> Cr-Commit-Position: refs/heads/main@{#914001}
FairyWorld · Aug 20, 2021 · 5ffcc86 · 5ffcc86
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diff --git a/docs/accessibility/figures/Makefile b/docs/accessibility/figures/Makefile
@@ -5,7 +5,13 @@ all: \
 	cover_flow.png \
 	single_process.png \
 	single_process_css_system.png \
-	single_process_system.png
+	single_process_system.png \
+	multi_process_browser.png \
+	multi_process_multiple_tabs.png \
+	other_multi_process_browser.png \
+	proxy_approach.png \
+	caching_approach.png \
+	multi_process_ax.png
 
 %.png: %.gv Makefile
 	dot -Tpng $< -o $@
diff --git a/docs/accessibility/figures/caching_approach.gv b/docs/accessibility/figures/caching_approach.gv
@@ -0,0 +1,51 @@
+digraph graphname {
+    graph [fontname = "helvetica", fontsize=11];
+    node [shape="box", fontname = "helvetica", fontsize=11];
+    edge [fontname = "helvetica", fontsize=11];
+    rankdir="TB";
+
+    subgraph cluster_browser {
+        label = "Browser Process";
+
+	subgraph cluster_cache_tree {
+		label = "Cached accessibility tree";
+		rankdir="TB";
+
+		root_cache [label="Root node"];
+		root_cache -> { button_cache, other_cache } [dir=none];
+		button_cache [label="Button node"];
+		other_cache [label="..."];
+	}
+    }
+
+    subgraph cluster_render {
+        label = "Render Process";
+
+	subgraph cluster_ax_tree {
+		label = "Accessibility tree";
+		rankdir="TB";
+
+		root_node [label="Root"];
+		root_node -> { button_node, other_node } [dir=none];
+		button_node [label="Button"];
+		other_node [label="..."];
+	}
+
+	subgraph cluster_dom_tree {
+		label = "DOM tree";
+		rankdir="TB";
+
+		root_dom_node [label="<body>"];
+		root_dom_node -> { button_dom_node, other_dom_node } [dir=none];
+		root_dom_node -> other_dom_node;
+		button_dom_node [label="<button>"];
+		other_dom_node [label="..."];
+	}
+
+    }
+
+    os [label="Operating System"];
+    os -> root_cache [dir=both];
+    root_cache -> root_node [dir=back, label="Atomic updates"];
+    root_node -> root_dom_node [dir=both];
+}
diff --git a/docs/accessibility/figures/caching_approach.png b/docs/accessibility/figures/caching_approach.png
diff --git a/docs/accessibility/figures/multi_process_ax.gv b/docs/accessibility/figures/multi_process_ax.gv
@@ -0,0 +1,40 @@
+digraph graphname {
+    graph [fontname = "helvetica", fontsize=11];
+    node [shape="box", fontname = "helvetica", fontsize=11];
+    edge [fontname = "helvetica", fontsize=11];
+    rankdir="RL";
+
+    subgraph cluster_browser {
+        label = "Browser Process";
+
+	subgraph cluster_browser_ax {
+		label = "BrowserAccessibilityManager";
+
+		ax_tree [label="AXTree"];
+	}
+    }
+
+    subgraph cluster_render {
+        label = "Render Process";
+
+	subgraph cluster_blink {
+		label = "Blink";
+
+		dom_node [label="Node"];
+		dom_node -> {layout_object, ax_object};
+		css [label="CSS"];
+		css -> layout_object;
+		layout_object [label="LayoutObject"];
+		layout_object -> ax_object;
+		ax_object [label="AXObject"];
+	}
+
+	render_ax [label="RenderAccessibilityImpl"];
+	ax_object -> render_ax;
+    }
+
+    render_ax -> ax_tree [label="AXTreeSerializer"];
+
+    ax_tree -> at [label="Platform\nAccessibility APIs"];
+    at [label="Assistive\nTechnology"];
+}
diff --git a/docs/accessibility/figures/multi_process_ax.png b/docs/accessibility/figures/multi_process_ax.png
diff --git a/docs/accessibility/figures/multi_process_browser.gv b/docs/accessibility/figures/multi_process_browser.gv
@@ -0,0 +1,23 @@
+digraph graphname {
+    graph [fontname = "helvetica", fontsize=11];
+    node [shape="box", fontname = "helvetica", fontsize=11];
+    edge [fontname = "helvetica", fontsize=11];
+    rankdir="RL";
+
+    subgraph cluster_renderer {
+        label = "Sandboxed Render Process";
+	web_page [label="Web Page Renderer (HTML, CSS, JS)"];
+    }
+
+    subgraph cluster_browser {
+        label = "Browser Process";
+	browser_window [label="Browser Window"];
+    }
+
+    browser_window -> web_page [label="User input events"];
+    web_page -> browser_window [label="Pixels"];
+
+    os [label="Operating System"];
+    os -> browser_window;
+    browser_window -> os;
+}
diff --git a/docs/accessibility/figures/multi_process_browser.png b/docs/accessibility/figures/multi_process_browser.png
diff --git a/docs/accessibility/figures/multi_process_multiple_tabs.gv b/docs/accessibility/figures/multi_process_multiple_tabs.gv
@@ -0,0 +1,46 @@
+digraph graphname {
+    graph [fontname = "helvetica", fontsize=11, compound=true];
+    node [shape="box", fontname = "helvetica", fontsize=11];
+    edge [fontname = "helvetica", fontsize=11];
+    rankdir="LR";
+
+    subgraph cluster_renderer1 {
+        label = "Render Process 1";
+	web_page1 [label="Web Page Renderer 1"];
+    }
+
+    subgraph cluster_renderer2 {
+        label = "Render Process 2";
+	web_page2 [label="Web Page Renderer 2"];
+	web_page3 [label="Web Page Renderer 3"];
+    }
+
+    subgraph cluster_renderer3 {
+        label = "Render Process 3";
+	web_page4 [label="Web Page Renderer 4"];
+    }
+
+    subgraph cluster_browser {
+        label = "Browser Process";
+
+        subgraph cluster_window1 {
+		label = "Browser Window";
+		tab1 [label="Tab 1"];
+		tab2 [label="Tab 2"];
+	}
+
+        subgraph cluster_window2 {
+		label = "Browser Window";
+		tab3 [label="Tab 3"];
+		tab4 [label="Tab 4"];
+	}
+    }
+
+    tab1 -> web_page1 [dir=both];
+    tab2 -> web_page2 [dir=both];
+    tab3 -> web_page3 [dir=both];
+    tab4 -> web_page4 [dir=both];
+
+    os [label="Operating System"];
+    os -> tab1 [lhead=cluster_browser, dir=both];
+}
diff --git a/docs/accessibility/figures/multi_process_multiple_tabs.png b/docs/accessibility/figures/multi_process_multiple_tabs.png
diff --git a/docs/accessibility/figures/other_multi_process_browser.gv b/docs/accessibility/figures/other_multi_process_browser.gv
@@ -0,0 +1,30 @@
+digraph graphname {
+    graph [fontname = "helvetica", fontsize=11, compound=true];
+    node [shape="box", fontname = "helvetica", fontsize=11];
+    edge [fontname = "helvetica", fontsize=11];
+    rankdir="LR";
+
+    subgraph cluster_browser {
+        label = "Browser Process";
+
+	window [label="Browser Window"];
+    }
+
+    subgraph cluster_tab1 {
+        label = "Tab Process 1";
+	tab1 [label="Tab 1"];
+    }
+
+    subgraph cluster_tab2 {
+        label = "Tab Process 2";
+	tab2 [label="Tab 2"];
+    }
+
+    window -> tab1 [dir=both];
+    window -> tab2 [dir=both];
+
+    os [label="Operating System"];
+    os -> window [lhead=cluster_browser, dir=both];
+    os -> tab1 [dir=both];
+    os -> tab2 [dir=both];
+}
diff --git a/docs/accessibility/figures/other_multi_process_browser.png b/docs/accessibility/figures/other_multi_process_browser.png
diff --git a/docs/accessibility/figures/proxy_approach.gv b/docs/accessibility/figures/proxy_approach.gv
@@ -0,0 +1,51 @@
+digraph graphname {
+    graph [fontname = "helvetica", fontsize=11];
+    node [shape="box", fontname = "helvetica", fontsize=11];
+    edge [fontname = "helvetica", fontsize=11];
+    rankdir="TB";
+
+    subgraph cluster_browser {
+        label = "Browser Process";
+
+	subgraph cluster_proxy_tree {
+		label = "Proxy accessibility tree";
+		rankdir="TB";
+
+		root_proxy [label="Root proxy"];
+		root_proxy -> { button_proxy, other_proxy } [dir=none];
+		button_proxy [label="Button proxy"];
+		other_proxy [label="..."];
+	}
+    }
+
+    subgraph cluster_render {
+        label = "Render Process";
+
+	subgraph cluster_ax_tree {
+		label = "Accessibility tree";
+		rankdir="TB";
+
+		root_node [label="Root"];
+		root_node -> { button_node, other_node } [dir=none];
+		button_node [label="Button"];
+		other_node [label="..."];
+	}
+
+	subgraph cluster_dom_tree {
+		label = "DOM tree";
+		rankdir="TB";
+
+		root_dom_node [label="<body>"];
+		root_dom_node -> { button_dom_node, other_dom_node } [dir=none];
+		root_dom_node -> other_dom_node;
+		button_dom_node [label="<button>"];
+		other_dom_node [label="..."];
+	}
+
+    }
+
+    os [label="Operating System"];
+    os -> root_proxy [dir=both];
+    root_proxy -> root_node [dir=both, label="Blocking IPC"];
+    root_node -> root_dom_node [dir=both];
+}
diff --git a/docs/accessibility/figures/proxy_approach.png b/docs/accessibility/figures/proxy_approach.png
diff --git a/docs/accessibility/figures/single_process_css_system.gv b/docs/accessibility/figures/single_process_css_system.gv
@@ -2,6 +2,7 @@ digraph graphname {
     graph [fontname = "helvetica", fontsize=11];
     node [shape="box", fontname = "helvetica", fontsize=11];
     edge [fontname = "helvetica", fontsize=11];
+    rankdir="RL";
 
     subgraph cluster_browser {
         label = "Browser";

diff --git a/docs/accessibility/figures/single_process_css_system.png b/docs/accessibility/figures/single_process_css_system.png
diff --git a/docs/accessibility/figures/single_process_system.gv b/docs/accessibility/figures/single_process_system.gv
@@ -2,6 +2,7 @@ digraph graphname {
     graph [fontname = "helvetica", fontsize=11];
     node [shape="box", fontname = "helvetica", fontsize=11];
     edge [fontname = "helvetica", fontsize=11];
+    rankdir="RL";
 
     subgraph cluster_browser {
         label = "Browser";

diff --git a/docs/accessibility/figures/single_process_system.png b/docs/accessibility/figures/single_process_system.png