ui: Fixed annotation hovering slow in code snippet view due to style calculation from setting stylesheets

bin/app/data/gui/code_view/code_view.css

@@ -117,10 +117,14 @@
 #code_file {
 	background-color: <color:code/snippet/background>;
 	margin-bottom: 0px;
-	border-bottom: 1px solid <color:code/file/background>; /* last file only */
+	border: none;
 	font-size: <setting:font_size>px;
 }
 
+#code_file[last=true] {
+	border-bottom: 1px solid <color:code/file/background>;
+}
+
 #title_bar, #title_bar_single {
 	background-color: <color:code/file/background>;
 	font-size: <setting:font_size>px;
@@ -186,6 +190,10 @@
 	font-size: <setting:font_size>px;
 }
 
+#code_file #code_snippet[first=true] {
+	border: none;
+}
+
 #code_file #code_snippet #scope_name, #code_file #code_snippet #dots {
 	background-color: <color:code/snippet/title/background>;
 	border: none;

src/lib_gui/qt/element/QtCodeFile.cpp

@@ -1,6 +1,7 @@
 #include "QtCodeFile.h"
 
 #include <QVBoxLayout>
+#include <QStyle>
 
 #include "MessageChangeFileView.h"
 
@@ -363,23 +364,15 @@ void QtCodeFile::updateSnippets()
 	int maxDigits = 1;
 	for (QtCodeSnippet* snippet : m_snippets)
 	{
-		if (snippet != m_snippets.front() && snippet->styleSheet().size())
-		{
-			snippet->setStyleSheet("");
-		}
-
 		maxDigits = qMax(maxDigits, snippet->lineNumberDigits());
 	}
 
 	for (QtCodeSnippet* snippet : m_snippets)
 	{
+		snippet->setProperty("first", snippet == m_snippets.front());
+		snippet->style()->polish(snippet); // recomputes style to make property take effect
 		snippet->updateLineNumberAreaWidthForDigits(maxDigits);
 	}
-
-	if (!m_snippets.front()->styleSheet().size())
-	{
-		m_snippets.front()->setStyleSheet("#code_snippet { border: none; }");
-	}
 }
 
 void QtCodeFile::updateTitleBar()

src/lib_gui/qt/element/QtCodeFileList.cpp

@@ -236,19 +236,10 @@ void QtCodeFileList::updateFiles()
 {
 	for (QtCodeFile* file : m_files)
 	{
-		if (file != m_files.back())
-		{
-			file->setStyleSheet("#code_file { border: none; }");
-		}
-
+		file->setProperty("last", file == m_files.back());
 		file->updateContent();
 	}
 
-	if (m_files.size())
-	{
-		m_files.back()->setStyleSheet("");
-	}
-
 	// Perform delayed so all widgets are already visible
 	QTimer::singleShot(100, this, &QtCodeFileList::updateSnippetTitleAndScrollBarSlot);
 }