Add FPDFTextObj_GetText() API

Generalize CPDF_TextPage::GetTextByRect(), so that it's possible to get
the text from a text page using a predicate, that way we can easily
get the text that belongs to single text object as well.

Change-Id: Ia457af0f41184694dc1481709be72b35685bce7f
Reviewed-on: https://pdfium-review.googlesource.com/39530
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

3 files changed, 64 insertions, 0 deletions

diff --git a/fpdfsdk/fpdf_edittext.cpp b/fpdfsdk/fpdf_edittext.cpp
index 6aa44b3b20..2773763b9a 100644
--- a/fpdfsdk/fpdf_edittext.cpp
+++ b/fpdfsdk/fpdf_edittext.cpp
@@ -22,6 +22,7 @@
 #include "core/fpdfapi/parser/cpdf_number.h"
 #include "core/fpdfapi/parser/cpdf_reference.h"
 #include "core/fpdfapi/parser/cpdf_stream.h"
+#include "core/fpdftext/cpdf_textpage.h"
 #include "core/fxcrt/fx_extension.h"
 #include "core/fxge/cfx_fontmgr.h"
 #include "core/fxge/fx_font.h"
@@ -564,6 +565,23 @@ FPDFTextObj_GetFontName(FPDF_PAGEOBJECT text,
   return dwStringLen;
 }
 
+FPDF_EXPORT unsigned long FPDF_CALLCONV
+FPDFTextObj_GetText(FPDF_PAGEOBJECT text_object,
+                    FPDF_TEXTPAGE text_page,
+                    void* buffer,
+                    unsigned long length) {
+  CPDF_TextObject* pTextObj = CPDFTextObjectFromFPDFPageObject(text_object);
+  if (!pTextObj)
+    return 0;
+
+  CPDF_TextPage* pTextPage = CPDFTextPageFromFPDFTextPage(text_page);
+  if (!pTextPage)
+    return 0;
+
+  WideString text = pTextPage->GetTextByObject(pTextObj);
+  return Utf16EncodeMaybeCopyAndReturnLength(text, buffer, length);
+}
+
 FPDF_EXPORT void FPDF_CALLCONV FPDFFont_Close(FPDF_FONT font) {
   CPDF_Font* pFont = CPDFFontFromFPDFFont(font);
   if (!pFont)
diff --git a/fpdfsdk/fpdf_text_embeddertest.cpp b/fpdfsdk/fpdf_text_embeddertest.cpp
index eafe1a2d11..bf064d672a 100644
--- a/fpdfsdk/fpdf_text_embeddertest.cpp
+++ b/fpdfsdk/fpdf_text_embeddertest.cpp
@@ -5,6 +5,7 @@
 #include <algorithm>
 #include <memory>
 #include <utility>
+#include <vector>
 
 #include "core/fxcrt/fx_memory.h"
 #include "public/cpp/fpdf_scopers.h"
@@ -762,6 +763,50 @@ TEST_F(FPDFTextEmbeddertest, CountRects) {
   UnloadPage(page);
 }
 
+TEST_F(FPDFTextEmbeddertest, GetText) {
+  ASSERT_TRUE(OpenDocument("hello_world.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_TRUE(page);
+
+  FPDF_TEXTPAGE text_page = FPDFText_LoadPage(page);
+  ASSERT_TRUE(text_page);
+
+  EXPECT_EQ(2, FPDFPage_CountObjects(page));
+  FPDF_PAGEOBJECT text_object = FPDFPage_GetObject(page, 0);
+  ASSERT_TRUE(text_object);
+
+  // Positive testing.
+  constexpr char kHelloText[] = "Hello, world!";
+  // Return value includes the terminating NUL that is provided.
+  constexpr unsigned long kHelloUTF16Size = FX_ArraySize(kHelloText) * 2;
+  constexpr wchar_t kHelloWideText[] = L"Hello, world!";
+  unsigned long size = FPDFTextObj_GetText(text_object, text_page, nullptr, 0);
+  ASSERT_EQ(kHelloUTF16Size, size);
+
+  std::vector<unsigned short> buffer(size);
+  ASSERT_EQ(size,
+            FPDFTextObj_GetText(text_object, text_page, buffer.data(), size));
+  ASSERT_EQ(kHelloWideText, GetPlatformWString(buffer.data()));
+
+  // Negative testing.
+  ASSERT_EQ(0U, FPDFTextObj_GetText(nullptr, text_page, nullptr, 0));
+  ASSERT_EQ(0U, FPDFTextObj_GetText(text_object, nullptr, nullptr, 0));
+  ASSERT_EQ(0U, FPDFTextObj_GetText(nullptr, nullptr, nullptr, 0));
+
+  // Buffer is too small, ensure it's not modified.
+  buffer.resize(2);
+  buffer[0] = 'x';
+  buffer[1] = '\0';
+  size =
+      FPDFTextObj_GetText(text_object, text_page, buffer.data(), buffer.size());
+  ASSERT_EQ(kHelloUTF16Size, size);
+  ASSERT_EQ('x', buffer[0]);
+  ASSERT_EQ('\0', buffer[1]);
+
+  FPDFText_ClosePage(text_page);
+  UnloadPage(page);
+}
+
 TEST_F(FPDFTextEmbeddertest, CroppedText) {
   static constexpr int kPageCount = 4;
   static constexpr FS_RECTF kBoxes[kPageCount] = {
diff --git a/fpdfsdk/fpdf_view_c_api_test.c b/fpdfsdk/fpdf_view_c_api_test.c
index 91d24fd233..56e9d7abed 100644
--- a/fpdfsdk/fpdf_view_c_api_test.c
+++ b/fpdfsdk/fpdf_view_c_api_test.c
@@ -206,6 +206,7 @@ int CheckPDFiumCApi() {
     CHK(FPDFPath_SetStrokeWidth);
     CHK(FPDFTextObj_GetFontName);
     CHK(FPDFTextObj_GetFontSize);
+    CHK(FPDFTextObj_GetText);
     CHK(FPDFText_GetMatrix);
     CHK(FPDFText_GetTextRenderMode);
     CHK(FPDFText_LoadFont);