Add private PPAPI interfaces for PDFium accessibility.

ppapi/c/private/ppb_pdf.h

Index: ppapi/c/private/ppb_pdf.h
diff --git a/ppapi/c/private/ppb_pdf.h b/ppapi/c/private/ppb_pdf.h
index a4c49c3e114315d46e9319bbc11a2c6aae3a68c6..f7dc3b469c2a04e89e37e3ada7ae68bd2213b8f2 100644
--- a/ppapi/c/private/ppb_pdf.h
+++ b/ppapi/c/private/ppb_pdf.h
@@ -9,6 +9,8 @@
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
+#include "ppapi/c/pp_point.h"
+#include "ppapi/c/pp_rect.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_var.h"
 #include "ppapi/c/private/pp_private_font_charset.h"
@@ -31,6 +33,44 @@ struct PP_PrivateFindResult {
   int length;
 };
 
+struct PP_PrivateAccessibilityViewportInfo {
+  double zoom;
+  struct PP_Point scroll;
+  struct PP_Point offset;
+};
+
+struct PP_PrivateAccessibilityDocInfo {
+  uint32_t page_count;
+  PP_Bool text_accessible;
+  PP_Bool text_copyable;
+};
+
+typedef enum {
+  PP_PRIVATEDIRECTION_NONE = 0,
+  PP_PRIVATEDIRECTION_LTR = 1,
+  PP_PRIVATEDIRECTION_RTL = 2,
+  PP_PRIVATEDIRECTION_TTB = 3,
+  PP_PRIVATEDIRECTION_BTT = 4,
+  PP_PRIVATEDIRECTION_LAST = PP_PRIVATEDIRECTION_BTT
+} PP_PrivateDirection;
+
+struct PP_PrivateAccessibilityPageInfo {
+  struct PP_Rect bounds;
+  uint32_t char_count;
+};
+
+struct PP_PrivateAccessibilityTextRunInfo {
+  uint32_t len;
+  double font_size;
+  struct PP_FloatRect bounds;
+  PP_PrivateDirection direction;
+};
+
+struct PP_PrivateAccessibilityCharInfo {
+  uint32_t unicode_character;
+  double char_width;
+};
+
 struct PPB_PDF {
   // Returns a resource identifying a font file corresponding to the given font
   // request after applying the browser-specific fallback.
@@ -95,6 +135,32 @@ struct PPB_PDF {
                                     int* natives_size_out,
                                     const char** snapshot_data_out,
                                     int* snapshot_size_out);
+
+  // Sends information about the viewport to the renderer for accessibility
+  // support.
+  void (*SetAccessibilityViewportInfo)(
+      PP_Instance instance,
+      struct PP_PrivateAccessibilityViewportInfo* viewport_info);
+
+  // Sends information about the PDF document to the renderer for accessibility
+  // support.
+  void (*SetAccessibilityDocInfo)(
+      PP_Instance instance,
+      struct PP_PrivateAccessibilityDocInfo* doc_info);
+
+  // Sends information about one page in a PDF document to the renderer for
+  // accessibility support.
+  void (*SetAccessibilityPageInfo)(
+      PP_Instance instance,
+      uint32_t page_index,

[raymes, 2016/05/17 20:38:40]

nit: could this go in PP_PrivateAccessibilityPageInfo?

[dmazzoni, 2016/05/26 21:59:13]

Done.

+      struct PP_PrivateAccessibilityPageInfo* page_info);

[raymes, 2016/05/17 20:38:40]

I wonder if it's good enough to put all the text runs into the PageInfo (and get
rid of the function which sets the text run info)? Do you think we could end up
with IPCs that are too big?

[dmazzoni, 2016/05/17 20:56:58]

Actually it just wasn't clear to me how to do this since this is a C API.
The IPC macros didn't seem to handle a C array of structs inside of a
struct, so it seemed cleaner to just use separate IPCs rather than
write custom Read/Write/Log functions for the IPC serializer.

[raymes, 2016/05/17 21:58:13]

Ah right. Yeah it is a bit of a headache, I agree. It also means doing more
memory management in the plugin for the complex struct. 

What if the function instead looked like:
SetAccessibilityPageInfo(PageInfo, TextRunInfo[], CharInfo[])

Where each TextRunInfo contains a start_index and end_index into the CharInfo
array?

In my opinion it would be better to consolidate this into one IPC/function call
though as sending the data on a per-page basis seems like a good granularity.

[dmazzoni, 2016/05/26 21:59:13]

Done.

+
+  void (*SetAccessibilityTextRunInfo)(

[raymes, 2016/05/17 20:38:40]

nit: no comment 

+      PP_Instance instance,
+      uint32_t page_index,
+      uint32_t text_run_index,
+      struct PP_PrivateAccessibilityTextRunInfo* text_run_info,
+      struct PP_PrivateAccessibilityCharInfo chars[]);

[raymes, 2016/05/17 20:38:40]

nit: could everything go in PP_PrivateAccessibilityTextRunInfo?

[dmazzoni, 2016/05/17 20:56:58]

Same - if this was C++ that's what I'd do.

 };
 
 #endif  // PPAPI_C_PRIVATE_PPB_PDF_H_