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Merged
bobsingor merged 1 commit into from
Nov 8, 2026
Merged

Read and write a page's viewports without loading the page #115

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5 changes: 5 additions & 0 deletions fpdfsdk/epdf_c_api_test.c
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Original file line number Diff line number Diff line change
Expand Up @@ -482,11 +482,16 @@ int CheckEmbedPDFCApi(void) {
CHK(EPDFNumberFormat_SetText);
CHK(EPDFNumberFormat_SetUnit);
CHK(EPDFPage_AddViewport);
CHK(EPDFPage_AddViewportRaw);
CHK(EPDFPage_CountViewports);
CHK(EPDFPage_CountViewportsRaw);
CHK(EPDFPage_FindViewport);
CHK(EPDFPage_GetViewport);
CHK(EPDFPage_GetViewportRaw);
CHK(EPDFPage_RemoveViewport);
CHK(EPDFPage_RemoveViewportRaw);
CHK(EPDFViewport_AddMeasure);
CHK(EPDFViewport_Close);
CHK(EPDFViewport_GetBBox);
CHK(EPDFViewport_GetMeasure);
CHK(EPDFViewport_GetName);
Expand Down
186 changes: 148 additions & 38 deletions fpdfsdk/epdf_measure.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,13 @@ struct OwnerEpochs {
// the same owner must invalidate one another. Direct annotations use
// page/index.
using OwnerKey = std::tuple<bool, uint32_t, int>;
struct Path;
struct Registry final : CPDF_MeasureStorage {
std::map<OwnerKey, OwnerEpochs> owners;
// The page behind each open raw viewport handle (EPDFPage_GetViewportRaw):
// built from the page dictionary and never parsed. Kept until
// EPDFViewport_Close, or until the document closes.
std::map<const Path*, RetainPtr<CPDF_Page>> raw_hosts;
};
struct Path {
Kind kind;
Expand Down Expand Up @@ -85,12 +90,14 @@ Arena* ArenaFor(Host* host) {
}
return static_cast<Arena*>(host->GetMeasureStorage());
}
OwnerEpochs* EpochsFor(CPDF_Page* page, CPDF_AnnotContext* annot) {
auto* doc = page->GetDocument();
Registry* RegistryFor(CPDF_Document* doc) {
if (!doc->GetMeasureStorage()) {
doc->SetMeasureStorage(std::make_unique<Registry>());
}
auto* registry = static_cast<Registry*>(doc->GetMeasureStorage());
return static_cast<Registry*>(doc->GetMeasureStorage());
}
OwnerEpochs* EpochsFor(CPDF_Page* page, CPDF_AnnotContext* annot) {
auto* registry = RegistryFor(page->GetDocument());
uint32_t obj =
annot ? annot->GetAnnotDict()->GetObjNum() : page->GetDict()->GetObjNum();
int direct_index = -1;
Expand Down Expand Up @@ -340,6 +347,79 @@ bool IsShape(const CPDF_AnnotContext* context) {
auto type = context->GetAnnotDict()->GetNameFor("Subtype");
return type == "Polygon" || type == "PolyLine";
}

// The page-level viewport functions, for a loaded page and for a raw host
// alike: each reads and writes only the page dictionary.
unsigned long CountViewports(const CPDF_Page* page) {
auto array = page->GetDict()->GetArrayFor("VP");
return array ? array->size() : 0;
}
Path* GetViewport(CPDF_Page* page, unsigned long index) {
auto array = page->GetDict()->GetArrayFor("VP");
if (!array || !array->GetDictAt(index)) {
return nullptr;
}
return ViewportPath(page, index);
}
Path* AddViewport(CPDF_Page* page, const FS_RECTF* bbox) {
if (!Finite(bbox)) {
return nullptr;
}
auto current = page->GetDict();
if (current->KeyExist("VP") && !current->GetArrayFor("VP")) {
return nullptr;
}
auto dict = page->GetMutableDict();
CPDF_Measure::DetachIndirect(dict.Get(), "VP");
auto array = dict->GetOrCreateArrayFor("VP");
auto viewport = array->AppendNew<CPDF_Dictionary>();
viewport->SetNewFor<CPDF_Name>("Type", "Viewport");
CFX_FloatRect rect(bbox->left, bbox->bottom, bbox->right, bbox->top);
rect.Normalize();
viewport->SetRectFor("BBox", rect);
return ViewportPath(page, array->size() - 1);
}
bool RemoveViewport(CPDF_Page* page, unsigned long index) {
auto current = page->GetDict()->GetArrayFor("VP");
if (!current || index >= current->size()) {
return false;
}
auto dict = page->GetMutableDict();
CPDF_Measure::DetachIndirect(dict.Get(), "VP");
auto array = dict->GetMutableArrayFor("VP");
array->RemoveAt(index);
if (array->IsEmpty()) {
dict->RemoveFor("VP");
}
auto* epochs = EpochsFor(page, nullptr);
++epochs->viewports;
epochs->measures.clear();
return true;
}

// A page built from its dictionary and never parsed, as EPDFPage_GetAnnotRaw
// builds one: what a raw viewport reads and writes through. Call it inside the
// document's view scope, so a layer resolves the page in the layer.
RetainPtr<CPDF_Page> RawHost(CPDF_Document* pdf, int page_index) {
if (!pdf || page_index < 0 || page_index >= pdf->GetPageCount()) {
return nullptr;
}
RetainPtr<const CPDF_Dictionary> dict = pdf->GetPageDictionary(page_index);
if (!dict || !CPDF_Document::IsPageTreeLeaf(dict.Get())) {
return nullptr;
}
return pdfium::MakeRetain<CPDF_Page>(
pdf, pdfium::WrapRetain(const_cast<CPDF_Dictionary*>(dict.Get())));
}
// A raw viewport handle keeps its host until EPDFViewport_Close. The host's
// arena holds the handle and every handle obtained through it.
EPDF_VIEWPORT KeepHost(RetainPtr<CPDF_Page> host, Path* path) {
if (!path) {
return nullptr;
}
RegistryFor(host->GetDocument())->raw_hosts[path] = std::move(host);
return reinterpret_cast<EPDF_VIEWPORT>(path);
}
} // namespace

FPDF_EXPORT EPDF_MEASURE FPDF_CALLCONV
Expand All @@ -365,60 +445,90 @@ EPDFAnnot_RemoveMeasure(FPDF_ANNOTATION annot) {
FPDF_EXPORT unsigned long FPDF_CALLCONV
EPDFPage_CountViewports(FPDF_PAGE page) {
ScopedFPDFPageView view(page);
auto array = view ? view.Get()->GetDict()->GetArrayFor("VP") : nullptr;
return array ? array->size() : 0;
return view ? CountViewports(view.Get()) : 0;
}
FPDF_EXPORT EPDF_VIEWPORT FPDF_CALLCONV
EPDFPage_GetViewport(FPDF_PAGE page, unsigned long index) {
ScopedFPDFPageView view(page);
auto array = view ? view.Get()->GetDict()->GetArrayFor("VP") : nullptr;
if (!array || !array->GetDictAt(index)) {
return nullptr;
}
return reinterpret_cast<EPDF_VIEWPORT>(ViewportPath(view.Get(), index));
return view ? reinterpret_cast<EPDF_VIEWPORT>(GetViewport(view.Get(), index))
: nullptr;
}
FPDF_EXPORT EPDF_VIEWPORT FPDF_CALLCONV
EPDFPage_AddViewport(FPDF_PAGE page, const FS_RECTF* bbox) {
if (!Finite(bbox)) {
return nullptr;
}
ScopedFPDFPageView view(page);
if (!view) {
return view ? reinterpret_cast<EPDF_VIEWPORT>(AddViewport(view.Get(), bbox))
: nullptr;
}
FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
EPDFPage_RemoveViewport(FPDF_PAGE page, unsigned long index) {
ScopedFPDFPageView view(page);
return view && RemoveViewport(view.Get(), index);
}
FPDF_EXPORT unsigned long FPDF_CALLCONV
EPDFPage_CountViewportsRaw(FPDF_DOCUMENT document, int page_index) {
CPDF_Document* pdf = CPDFDocumentFromFPDFDocument(document);
if (!pdf || page_index < 0 || page_index >= pdf->GetPageCount()) {
return 0;
}
CPDF_DocumentViewScope document_view(pdf);
RetainPtr<const CPDF_Dictionary> dict = pdf->GetPageDictionary(page_index);
auto array = dict ? dict->GetArrayFor("VP") : nullptr;
return array ? array->size() : 0;
}
FPDF_EXPORT EPDF_VIEWPORT FPDF_CALLCONV
EPDFPage_GetViewportRaw(FPDF_DOCUMENT document,
int page_index,
unsigned long index) {
CPDF_Document* pdf = CPDFDocumentFromFPDFDocument(document);
CPDF_DocumentViewScope document_view(pdf);
auto host = RawHost(pdf, page_index);
if (!host) {
return nullptr;
}
auto current = view.Get()->GetDict();
if (current->KeyExist("VP") && !current->GetArrayFor("VP")) {
Path* path = GetViewport(host.Get(), index);
return KeepHost(std::move(host), path);
}
FPDF_EXPORT EPDF_VIEWPORT FPDF_CALLCONV
EPDFPage_AddViewportRaw(FPDF_DOCUMENT document,
int page_index,
const FS_RECTF* bbox) {
CPDF_Document* pdf = CPDFDocumentFromFPDFDocument(document);
CPDF_DocumentViewScope document_view(pdf);
auto host = RawHost(pdf, page_index);
if (!host) {
return nullptr;
}
auto dict = view.Get()->GetMutableDict();
CPDF_Measure::DetachIndirect(dict.Get(), "VP");
auto array = dict->GetOrCreateArrayFor("VP");
auto viewport = array->AppendNew<CPDF_Dictionary>();
viewport->SetNewFor<CPDF_Name>("Type", "Viewport");
CFX_FloatRect rect(bbox->left, bbox->bottom, bbox->right, bbox->top);
rect.Normalize();
viewport->SetRectFor("BBox", rect);
return reinterpret_cast<EPDF_VIEWPORT>(
ViewportPath(view.Get(), array->size() - 1));
Path* path = AddViewport(host.Get(), bbox);
return KeepHost(std::move(host), path);
}
FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
EPDFPage_RemoveViewport(FPDF_PAGE page, unsigned long index) {
ScopedFPDFPageView view(page);
auto current = view ? view.Get()->GetDict()->GetArrayFor("VP") : nullptr;
if (!current || index >= current->size()) {
return false;
EPDFPage_RemoveViewportRaw(FPDF_DOCUMENT document,
int page_index,
unsigned long index) {
CPDF_Document* pdf = CPDFDocumentFromFPDFDocument(document);
CPDF_DocumentViewScope document_view(pdf);
auto host = RawHost(pdf, page_index);
return host && RemoveViewport(host.Get(), index);
}
FPDF_EXPORT void FPDF_CALLCONV EPDFViewport_Close(EPDF_VIEWPORT viewport) {
const auto* path = reinterpret_cast<const Path*>(viewport);
auto* storage =
path ? path->page->GetDocument()->GetMeasureStorage() : nullptr;
if (!storage) {
return;
}
auto dict = view.Get()->GetMutableDict();
CPDF_Measure::DetachIndirect(dict.Get(), "VP");
auto array = dict->GetMutableArrayFor("VP");
array->RemoveAt(index);
if (array->IsEmpty()) {
dict->RemoveFor("VP");
auto& hosts = static_cast<Registry*>(storage)->raw_hosts;
auto it = hosts.find(path);
// A loaded page's viewport: the page owns it.
if (it == hosts.end()) {
return;
}
auto* epochs = EpochsFor(view.Get(), nullptr);
++epochs->viewports;
epochs->measures.clear();
return true;
// The host goes when this returns, with its arena and every path in it.
RetainPtr<CPDF_Page> host = std::move(it->second);
hosts.erase(it);
}
FPDF_EXPORT int FPDF_CALLCONV EPDFPage_FindViewport(FPDF_PAGE page,
const FS_POINTF* point) {
Expand Down
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