From a43bae5fe45b7441fbe0e272dfc7d3727d280e53 Mon Sep 17 00:00:00 2001
From: Jonas Kümmerlin <jonas@kuemmerlin.eu>
Date: Sun, 7 Jun 2020 15:13:58 +0200
Subject: notebook: skip drawing tabs where the whole thing would be clipped
 anyway

---
 alf/alfnotebook.cpp | 55 +++++++++++++++++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 19 deletions(-)

diff --git a/alf/alfnotebook.cpp b/alf/alfnotebook.cpp
index f6ae937..96e188f 100644
--- a/alf/alfnotebook.cpp
+++ b/alf/alfnotebook.cpp
@@ -354,11 +354,16 @@ ALF_Notebook_AppendPage(ALFNotebookPriv *priv, const TCHAR *title)
     return page;
 }
 
+static BOOL
+ALF_Notebook_DoRectsIntersect(const RECT *rc1, const RECT *rc2)
+{
+    return rc1->left < rc2->right && rc2->left < rc1->right
+        && rc1->top < rc2->bottom && rc2->top < rc1->bottom;
+}
+
 static void
 ALF_Notebook_SwitcherPaint(ALFNotebookPriv *priv, HDC dc, RECT *rcDraw)
 {
-    (void)rcDraw; // TODO: restrict some of our drawing to the invalidation rect
-
     ALF_Notebook_ValidateTabRects(priv);
 
     HFONT oldfont = SelectFont(dc, priv->font);
@@ -373,23 +378,29 @@ ALF_Notebook_SwitcherPaint(ALFNotebookPriv *priv, HDC dc, RECT *rcDraw)
     COLORREF clrBtnText = GetSysColor(COLOR_BTNTEXT);
 
     if (!priv->selectedPage || priv->pages.next != &priv->selectedPage->list) {
-        RECT rcLeftTop = { 0,
-                           ALF_Notebook_SwitcherHeight(priv) - 1,
-                           2,
-                           ALF_Notebook_SwitcherHeight(priv) };
-        DrawEdge(dc, &rcLeftTop, EDGE_RAISED, BF_SOFT|BF_TOPLEFT);
-
-        RECT rcLeftSpace = { 0,
-                             0,
-                             rcLeftTop.right,
-                             rcLeftTop.top };
-        FillRect(dc, &rcLeftSpace, hbrBtnFace);
+        RECT rcLeftTopClip = { 0, 0, 2, rcClient.bottom - rcClient.top };
+        if (ALF_Notebook_DoRectsIntersect(&rcLeftTopClip, rcDraw)) {
+            RECT rcLeftTop = { 0,
+                            rcClient.bottom - rcClient.top - 1,
+                            2,
+                            rcClient.bottom - rcClient.top };
+            DrawEdge(dc, &rcLeftTop, EDGE_RAISED, BF_SOFT|BF_TOPLEFT);
+
+            RECT rcLeftSpace = { 0,
+                                0,
+                                rcLeftTop.right,
+                                rcLeftTop.top };
+            FillRect(dc, &rcLeftSpace, hbrBtnFace);
+        }
     }
 
     ALF_FOR_LIST(ALFNotebookPage, list, &priv->pages, p) {
         RECT r = p->calculatedTabRect;
 
         if (p != priv->selectedPage) {
+            if (!ALF_Notebook_DoRectsIntersect(&r, rcDraw))
+                continue; // FIXME! correct clip rect calculation when next to active tab
+
             RECT rBottom = { r.left + 2,
                              r.bottom - 1,
                              r.right - 2,
@@ -444,6 +455,9 @@ ALF_Notebook_SwitcherPaint(ALFNotebookPriv *priv, HDC dc, RECT *rcDraw)
         } else {
             InflateRect(&r, 2, 0);
 
+            if (!ALF_Notebook_DoRectsIntersect(&r, rcDraw))
+                continue;
+
             RECT rLeft =  { r.left,
                             r.top + 2,
                             r.left + 2,
@@ -505,19 +519,22 @@ ALF_Notebook_SwitcherPaint(ALFNotebookPriv *priv, HDC dc, RECT *rcDraw)
         }
     }
 
-    RECT rcRightTop = { priv->totalSwitcherWidth, ALF_Notebook_SwitcherHeight(priv) - 1,
-        rcClient.right-rcClient.left, ALF_Notebook_SwitcherHeight(priv) };
+    RECT rcRightTop = { priv->totalSwitcherWidth, rcClient.bottom - rcClient.top - 1,
+        rcClient.right-rcClient.left, rcClient.bottom - rcClient.top };
 
     if (!priv->selectedPage || priv->pages.prev != &priv->selectedPage->list) {
         rcRightTop.left -= 2;
     }
 
     if (rcRightTop.left < rcRightTop.right) {
-        DrawEdge(dc, &rcRightTop, EDGE_RAISED, BF_SOFT|BF_TOPRIGHT);
+        RECT rcRightTopClip = { rcRightTop.left, 0, rcClient.right-rcClient.left, rcClient.bottom-rcClient.top };
+        if (ALF_Notebook_DoRectsIntersect(&rcRightTopClip, rcDraw)) {
+            DrawEdge(dc, &rcRightTop, EDGE_RAISED, BF_SOFT|BF_TOPRIGHT);
 
-        RECT rcRightSpace = { rcRightTop.left, 0,
-                              rcRightTop.right, rcRightTop.top };
-        FillRect(dc, &rcRightSpace, GetSysColorBrush(COLOR_BTNFACE));
+            RECT rcRightSpace = { rcRightTop.left, 0,
+                                rcRightTop.right, rcRightTop.top };
+            FillRect(dc, &rcRightSpace, GetSysColorBrush(COLOR_BTNFACE));
+        }
     }
 
     SelectFont(dc, oldfont);
-- 
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