Gemini: count the App's per-line tables in the page budget

Found in M3 while checking floors with the radio on: a windowed page left
1.5 to 3 KB less than the 40 KB steady floor (Q86), radio or not. The
budget counted TextBuffer's index (8 B/line) but not the App's tables,
which also grew by doubling. Now 16 B/line, and the App sizes them
exactly. The FAQ (1051 lines, windowed): 38.5 -> 39.6 KB after, radio
asleep; 37.1 -> 39.0 KB with the radio listening.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/apps/gemini_app.cpp

@@ -103,8 +103,11 @@ void GeminiApp::show(GeminiPage&& page) {
 }
 
 void GeminiApp::analyse() {
-    types_.clear();
-    links_.clear();
+    // Sized exactly: the Service budgeted these bytes per line (kBytesPerLine), growth by
+    // doubling would take up to twice that.
+    std::vector<uint8_t>().swap(types_);
+    std::vector<uint32_t>().swap(links_);
+    types_.reserve(page_.text.lineCount());
     // A window may start inside a preformatted block: the index says (bit 31).
     size_t entry = page_.windowStart / GeminiService::kIndexEvery;
     bool pre = page_.windowed && entry < page_.lineIndex.size() && (page_.lineIndex[entry] & 0x80000000u);
@@ -114,6 +117,7 @@ void GeminiApp::analyse() {
         types_.push_back(static_cast<uint8_t>(t));
         if (t == LineType::Link) links_.push_back(i);
     }
+    links_.shrink_to_fit();
     layoutDirty_ = true;
     requestRedraw();
 }

src/services/gemini_service.cpp

@@ -192,7 +192,7 @@ bool GeminiService::loadWindow(const GeminiPage& page, size_t firstLine) {
     windowPage_.lineIndex = page.lineIndex;
     windowLine_ = firstLine;
     // The App drops its current window once the new one is in: count that memory as coming back.
-    windowReleasing_ = page.text.bytes() + page.text.lineCount() * 8;
+    windowReleasing_ = page.text.bytes() + page.text.lineCount() * kBytesPerLine;
     return start(Job::Window);
 }
 
@@ -618,7 +618,7 @@ void GeminiService::fetchOne(const std::string& url, GeminiPage& page, bool load
         // what was free before minus the steady floor; meanwhile the heap must stay above the
         // transient floor. Both counted with the next 4 KB chunk and the line index.
         size_t take = std::min<size_t>(n - i, kMaxBody - page.text.bytes());
-        size_t pageCost = page.text.bytes() + page.text.lineCount() * 8 + TextBuffer::kChunk + take;
+        size_t pageCost = page.text.bytes() + page.text.lineCount() * kBytesPerLine + TextBuffer::kChunk + take;
         if (take < static_cast<size_t>(n - i)) page.truncatedWhy = "longer than 64 KB";
         else if (freeBefore < kSteadyFloor + pageCost) page.truncatedWhy = "not enough memory to keep it";
         else if (esp_get_free_heap_size() < kTransientFloor + TextBuffer::kChunk + take)
@@ -720,7 +720,7 @@ void GeminiService::loadFromCard(GeminiPage& page, size_t freeBefore, const std:
             if (page.totalLines % kIndexEvery == 0) page.lineIndex.push_back(lineStart | (pre ? 0x80000000u : 0));
             if (line.compare(0, 3, "```") == 0) pre = !pre;
             if (loading) {
-                if (page.text.bytes() + page.text.lineCount() * 8 + line.size() + 1 > budget) loading = false;
+                if (page.text.bytes() + page.text.lineCount() * kBytesPerLine + line.size() + 1 > budget) loading = false;
                 else {
                     line += '\n';
                     page.text.append(line.data(), line.size());
@@ -768,7 +768,7 @@ void GeminiService::readWindow(GeminiPage& page, size_t firstLine, size_t budget
                     continue;
                 }
                 if (lineNo >= firstLine) {
-                    if (page.text.bytes() + page.text.lineCount() * 8 + line.size() + 1 > budget) done = true;
+                    if (page.text.bytes() + page.text.lineCount() * kBytesPerLine + line.size() + 1 > budget) done = true;
                     else {
                         line += '\n';
                         page.text.append(line.data(), line.size());

src/services/gemini_service.h

@@ -64,6 +64,10 @@ class GeminiService {
     static constexpr int kMaxLinkedPages = 30;           // Q83
     static constexpr size_t kIndexEvery = 64;            // lines between lineIndex entries
     static constexpr size_t kMaxLineBytes = 8192;        // longer lines are cut
+    // What a page costs per line on top of its text: TextBuffer's index (8) and the App's tables
+    // (type, first row, links: about 8). Counting only the first left the steady floor 1.5 to 3 KB
+    // short on a windowed page (found in M3).
+    static constexpr size_t kBytesPerLine = 16;
     static constexpr const char* kBookmarks = "/gemini/bookmarks.gmi";
     static constexpr const char* kStartUrl = "about:start";