Rework progressive render loop.

core/src/fpdfapi/fpdf_render/fpdf_render.cpp

Index: core/src/fpdfapi/fpdf_render/fpdf_render.cpp
diff --git a/core/src/fpdfapi/fpdf_render/fpdf_render.cpp b/core/src/fpdfapi/fpdf_render/fpdf_render.cpp
index 35d62ce0b3d6eebba3d396d47972a20c3e41e133..d0f4eee354e3b21ba1c9ef6aa760ff950ae4ef39 100644
--- a/core/src/fpdfapi/fpdf_render/fpdf_render.cpp
+++ b/core/src/fpdfapi/fpdf_render/fpdf_render.cpp
@@ -4,7 +4,7 @@
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
-#include "render_int.h"
+#include "core/src/fpdfapi/fpdf_render/render_int.h"
 
 #include "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_render.h"
@@ -1039,9 +1039,8 @@ CPDF_ProgressiveRenderer::CPDF_ProgressiveRenderer(
       m_pOptions(pOptions),
       m_LayerIndex(0),
       m_ObjectIndex(0),
-      m_ObjectPos(nullptr),
-      m_PrevLastPos(nullptr) {
-}
+      m_pCurrentLayer(nullptr),
+      m_LastObjectRendered(nullptr) {}
 
 CPDF_ProgressiveRenderer::~CPDF_ProgressiveRenderer() {
   if (m_pRenderStatus)
@@ -1058,66 +1057,44 @@ void CPDF_ProgressiveRenderer::Start(IFX_Pause* pPause) {
 }
 
 void CPDF_ProgressiveRenderer::Continue(IFX_Pause* pPause) {
-  if (m_Status != ToBeContinued) {
-    return;
-  }
-  FX_DWORD nLayers = m_pContext->CountLayers();
-  for (; m_LayerIndex < nLayers; m_LayerIndex++) {
-    CPDF_RenderContext::Layer* pLayer = m_pContext->GetLayer(m_LayerIndex);
-    FX_POSITION LastPos = pLayer->m_pObjectList->GetLastObjectPosition();
-    if (!m_ObjectPos) {
-      if (LastPos == m_PrevLastPos) {
-        if (!pLayer->m_pObjectList->IsParsed()) {
-          pLayer->m_pObjectList->ContinueParse(pPause);
-          if (!pLayer->m_pObjectList->IsParsed()) {
-            return;
-          }
-          LastPos = pLayer->m_pObjectList->GetLastObjectPosition();
-        }
+  IPDF_RenderModule* pModule = CPDF_ModuleMgr::Get()->GetRenderModule();
+  int nStepLimit = pModule->GetConfig()->m_RenderStepLimit;
+  while (m_Status == ToBeContinued) {
+    if (!m_pCurrentLayer) {
+      if (m_LayerIndex >= m_pContext->CountLayers()) {
+        m_Status = Done;
+        return;
       }
-      if (LastPos == m_PrevLastPos) {
-        if (m_pRenderStatus) {
-          m_pRenderStatus.reset();
-          m_pDevice->RestoreState();
-          m_ObjectPos = NULL;
-          m_PrevLastPos = NULL;
-        }
-        continue;
-      }
-      if (m_PrevLastPos) {
-        m_ObjectPos = m_PrevLastPos;
-        pLayer->m_pObjectList->GetNextObject(m_ObjectPos);
-      } else {
-        m_ObjectPos = pLayer->m_pObjectList->GetFirstObjectPosition();
-      }
-      m_PrevLastPos = LastPos;
-    }
-    if (!m_pRenderStatus) {
-      m_ObjectPos = pLayer->m_pObjectList->GetFirstObjectPosition();
+      m_pCurrentLayer = m_pContext->GetLayer(m_LayerIndex);
+      m_LastObjectRendered = nullptr;
       m_ObjectIndex = 0;
       m_pRenderStatus.reset(new CPDF_RenderStatus());
       m_pRenderStatus->Initialize(
           m_pContext, m_pDevice, NULL, NULL, NULL, NULL, m_pOptions,
-          pLayer->m_pObjectList->m_Transparency, FALSE, NULL);
+          m_pCurrentLayer->m_pObjectList->m_Transparency, FALSE, NULL);
       m_pDevice->SaveState();
       m_ClipRect = m_pDevice->GetClipBox();
       CFX_Matrix device2object;
-      device2object.SetReverse(pLayer->m_Matrix);
+      device2object.SetReverse(m_pCurrentLayer->m_Matrix);
       device2object.TransformRect(m_ClipRect);
     }
-    int objs_to_go = CPDF_ModuleMgr::Get()
-                         ->GetRenderModule()
-                         ->GetConfig()
-                         ->m_RenderStepLimit;
-    while (m_ObjectPos) {
+    FX_POSITION pos;
+    if (m_LastObjectRendered) {
+      pos = m_LastObjectRendered;
+      m_pCurrentLayer->m_pObjectList->GetNextObject(pos);
+    } else {
+      pos = m_pCurrentLayer->m_pObjectList->GetFirstObjectPosition();
+    }
+    int nObjsToGo = nStepLimit;
+    while (pos) {
       CPDF_PageObject* pCurObj =
-          pLayer->m_pObjectList->GetObjectAt(m_ObjectPos);
+          m_pCurrentLayer->m_pObjectList->GetObjectAt(pos);
       if (pCurObj && pCurObj->m_Left <= m_ClipRect.right &&
           pCurObj->m_Right >= m_ClipRect.left &&
           pCurObj->m_Bottom <= m_ClipRect.top &&
           pCurObj->m_Top >= m_ClipRect.bottom) {
-        if (m_pRenderStatus->ContinueSingleObject(pCurObj, &pLayer->m_Matrix,
-                                                  pPause)) {
+        if (m_pRenderStatus->ContinueSingleObject(
+                pCurObj, &m_pCurrentLayer->m_Matrix, pPause)) {
           return;
         }
         if (pCurObj->m_Type == CPDF_PageObject::IMAGE &&
@@ -1127,37 +1104,37 @@ void CPDF_ProgressiveRenderer::Continue(IFX_Pause* pPause) {
         }
         if (pCurObj->m_Type == CPDF_PageObject::FORM ||
             pCurObj->m_Type == CPDF_PageObject::SHADING) {
-          objs_to_go = 0;
+          nObjsToGo = 0;
         } else {
-          objs_to_go--;
+          --nObjsToGo;
         }
       }
       m_ObjectIndex++;
-      pLayer->m_pObjectList->GetNextObject(m_ObjectPos);
-      if (objs_to_go == 0) {
-        if (pPause && pPause->NeedToPauseNow()) {
+      m_LastObjectRendered = pos;
+      if (nObjsToGo == 0) {
+        if (pPause && pPause->NeedToPauseNow())
           return;
-        }
-        objs_to_go = CPDF_ModuleMgr::Get()
-                         ->GetRenderModule()
-                         ->GetConfig()
-                         ->m_RenderStepLimit;
+        nObjsToGo = nStepLimit;
       }
+      m_pCurrentLayer->m_pObjectList->GetNextObject(pos);
     }
-    if (!pLayer->m_pObjectList->IsParsed()) {
-      return;
-    }
-    m_pRenderStatus.reset();
-    m_pDevice->RestoreState();
-    m_ObjectPos = NULL;
-    m_PrevLastPos = NULL;
-    if (pPause && pPause->NeedToPauseNow()) {
+    if (m_pCurrentLayer->m_pObjectList->IsParsed()) {
+      m_pRenderStatus.reset();
+      m_pDevice->RestoreState();
+      m_pCurrentLayer = nullptr;
+      m_LastObjectRendered = nullptr;
       m_LayerIndex++;
-      return;
+      if (pPause && pPause->NeedToPauseNow()) {
+        return;
+      }
+    } else {
+      m_pCurrentLayer->m_pObjectList->ContinueParse(pPause);
+      if (!m_pCurrentLayer->m_pObjectList->IsParsed())
+        return;
     }
   }
-  m_Status = Done;
 }
+
 int CPDF_ProgressiveRenderer::EstimateProgress() {
   if (!m_pContext) {
     return 0;