Performance improvements during layout calculation (#122)

* Performance improvements during layout calculation Both `invalidateSectionMaxYsCacheForSectionIndices` and `invalidateEntireSectionMaxYsCache` do linear passes. These are called on each section header, section footer and background. Leading to a lot of work being done with long lists. This PR short circuits the work if we try to remove header, footers and backgrounds that don't exist. A better option would be to run the calls above once per update vs per update item. That would require a bit more rework though. * Update MagazineLayout/LayoutCore/ModelState.swift Co-authored-by: Bryan Keller <[email protected]> * Update MagazineLayout/LayoutCore/ModelState.swift Co-authored-by: Bryan Keller <[email protected]> * Update MagazineLayout/LayoutCore/ModelState.swift Co-authored-by: Bryan Keller <[email protected]> --------- Co-authored-by: Elfred Pagan <[email protected]> Co-authored-by: Bryan Keller <[email protected]>
airbnb · Mar 4, 2024 · 2d0d4f9 · 2d0d4f9
1 parent bfc6077
commit 2d0d4f9
Show file tree

Hide file tree

Showing 2 changed files with 27 additions and 23 deletions.
diff --git a/MagazineLayout/LayoutCore/ModelState.swift b/MagazineLayout/LayoutCore/ModelState.swift
@@ -593,11 +593,10 @@ final class ModelState {
   }
 
   func removeHeader(forSectionAtIndex sectionIndex: Int) {
-    currentSectionModels[sectionIndex].removeHeader()
-
-    invalidateSectionMaxYsCacheForSectionIndices(startingAt: sectionIndex)
-
-    prepareElementLocationsForFlattenedIndices()
+    if currentSectionModels[sectionIndex].removeHeader() {
+      invalidateSectionMaxYsCacheForSectionIndices(startingAt: sectionIndex)
+      prepareElementLocationsForFlattenedIndices()
+    }
   }
 
   func setFooter(_ footerModel: FooterModel, forSectionAtIndex sectionIndex: Int) {
@@ -609,11 +608,10 @@ final class ModelState {
   }
 
   func removeFooter(forSectionAtIndex sectionIndex: Int) {
-    currentSectionModels[sectionIndex].removeFooter()
-
-    invalidateSectionMaxYsCacheForSectionIndices(startingAt: sectionIndex)
-
-    prepareElementLocationsForFlattenedIndices()
+    if currentSectionModels[sectionIndex].removeFooter() {
+      invalidateSectionMaxYsCacheForSectionIndices(startingAt: sectionIndex)
+      prepareElementLocationsForFlattenedIndices()
+    }
   }
 
   func setBackground(
@@ -626,9 +624,9 @@ final class ModelState {
   }
 
   func removeBackground(forSectionAtIndex sectionIndex: Int) {
-    currentSectionModels[sectionIndex].removeBackground()
-
-    prepareElementLocationsForFlattenedIndices()
+    if currentSectionModels[sectionIndex].removeBackground() {
+      prepareElementLocationsForFlattenedIndices()
+    }
   }
 
   func setSections(_ sectionModels: [SectionModel]) {

diff --git a/MagazineLayout/LayoutCore/SectionModel.swift b/MagazineLayout/LayoutCore/SectionModel.swift
@@ -247,20 +247,22 @@ struct SectionModel {
     }
   }
 
-  mutating func removeHeader() {
-    if let indexOfHeader = indexOfHeaderRow() {
-      updateIndexOfFirstInvalidatedRowIfNecessary(toProposedIndex: indexOfHeader)
+  mutating func removeHeader() -> Bool {
+    guard let indexOfHeader = indexOfHeaderRow() else {
+      return false
     }
-
+    updateIndexOfFirstInvalidatedRowIfNecessary(toProposedIndex: indexOfHeader)
     headerModel = nil
+    return true
   }
 
-  mutating func removeFooter() {
-    if let indexOfFooter = indexOfFooterRow() {
-      updateIndexOfFirstInvalidatedRowIfNecessary(toProposedIndex: indexOfFooter)
+  mutating func removeFooter() -> Bool {
+    guard let indexOfFooter = indexOfFooterRow() else {
+      return false
     }
-
+    updateIndexOfFirstInvalidatedRowIfNecessary(toProposedIndex: indexOfFooter)
     footerModel = nil
+    return true
   }
 
   mutating func updateItemHeight(toPreferredHeight preferredHeight: CGFloat, atIndex index: Int) {
@@ -334,9 +336,13 @@ struct SectionModel {
     // No need to invalidate since the background doesn't affect the layout.
   }
 
-  mutating func removeBackground() {
-    backgroundModel = nil
+  mutating func removeBackground() -> Bool {
+    guard backgroundModel != nil else {
+      return false
+    }
+    self.backgroundModel = nil
     // No need to invalidate since the background doesn't affect the layout.
+    return true
   }
 
   // MARK: Private