From ef10d110989eb36f34925d31e4cdb4452da15fca Mon Sep 17 00:00:00 2001
From: Joshua Goins <josh@redstrate.com>
Date: Mon, 21 Nov 2022 11:40:05 -0500
Subject: [PATCH] Insert more error checks

---
 SilicaViewer/SilicaEngine.swift | 46 +++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 16 deletions(-)

diff --git a/SilicaViewer/SilicaEngine.swift b/SilicaViewer/SilicaEngine.swift
index 82f2a9a..ea530b7 100644
--- a/SilicaViewer/SilicaEngine.swift
+++ b/SilicaViewer/SilicaEngine.swift
@@ -43,9 +43,11 @@ class SilicaEngine {
                 
                 var maskContext: CGContext?
                 
-                let kernel = getBlendKernel(layer)
+                guard let kernel = getBlendKernel(layer) else {
+                    return nil
+                }
                 
-                if layer.mask != nil {
+                if let mask = layer.mask {
                     let grayColorSpace = CGColorSpaceCreateDeviceGray()
                     let maskBitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue).union(.byteOrder16Big)
                     
@@ -60,7 +62,7 @@ class SilicaEngine {
                     maskContext?.setFillColor(.white)
                     maskContext?.fill(document.cgRect())
                     
-                    for chunk in layer.mask!.chunks {
+                    for chunk in mask.chunks {
                         if let image = chunk.image {
                             maskContext?.draw(image, in: document.getChunkRect(chunk))
                         }
@@ -72,7 +74,9 @@ class SilicaEngine {
                     layerContext?.setBlendMode(.normal)
                     
                     if !layer.data.hidden {
-                        layerContext?.draw(chunk.image!, in: document.getChunkRect(chunk))
+                        if let image = chunk.image {
+                            layerContext?.draw(image, in: document.getChunkRect(chunk))
+                        }
                     }
                 }
                 
@@ -83,9 +87,9 @@ class SilicaEngine {
                     var clippedMaster: CGImage? = layerImage
                     for layer in clippingLayers {
                         // so we if we want to clip, we want to gather all of the clipping layers in order first...
-                        let temporaryClippedMaster = blendLayer(document: document, layer: layer, previousImage: &clippedMaster)
-                        
-                        clippedMaster = context.createCGImage(temporaryClippedMaster, from: document.cgRect(), format: .RGBA8, colorSpace: document.colorSpace)
+                        if let temporaryClippedMaster = blendLayer(document: document, layer: layer, previousImage: &clippedMaster) {
+                            clippedMaster = context.createCGImage(temporaryClippedMaster, from: document.cgRect(), format: .RGBA8, colorSpace: document.colorSpace)
+                        }
                     }
                     
                     layerContext?.setAlpha(1.0)
@@ -106,7 +110,9 @@ class SilicaEngine {
                 }
                 
                 // apply image
-                masterImage = kernel!.apply(foreground: CIImage(cgImage: previousImage!), background: masterImage, colorSpace: document.colorSpace)!
+                masterImage = kernel.apply(foreground: CIImage(cgImage: previousImage!),
+                                           background: masterImage,
+                                           colorSpace: document.colorSpace)!
             }
         }
         
@@ -116,7 +122,7 @@ class SilicaEngine {
     func makeBlendImage(document: SilicaDocument, layer: SilicaLayer) -> CGImage {
         var maskContext: CGContext?
         
-        if layer.mask != nil {
+        if let mask = layer.mask {
             let grayColorSpace = CGColorSpaceCreateDeviceGray()
             let maskBitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue).union(.byteOrder16Big)
             
@@ -131,8 +137,10 @@ class SilicaEngine {
             maskContext?.setFillColor(.white)
             maskContext?.fill(document.cgRect())
             
-            for chunk in layer.mask!.chunks {
-                maskContext?.draw(chunk.image!, in: document.getChunkRect(chunk))
+            for chunk in mask.chunks {
+                if let image = chunk.image {
+                    maskContext?.draw(image, in: document.getChunkRect(chunk))
+                }
             }
         }
         
@@ -161,7 +169,9 @@ class SilicaEngine {
             layerContext?.setBlendMode(.normal)
             
             if !layer.hidden {
-                layerContext?.draw(chunk.image!, in: document.getChunkRect(chunk))
+                if let image = chunk.image {
+                    layerContext?.draw(image, in: document.getChunkRect(chunk))
+                }
             }
         }
         
@@ -173,7 +183,7 @@ class SilicaEngine {
     ///   - layer: The `SilicaLayer` to draw.
     ///   - previousImage: Previous `CGImage` to draw on top of, can be null.
     /// - Returns: A `CIImage` of the new image.
-    func blendLayer(document: SilicaDocument, layer : SilicaLayer, previousImage : inout CGImage?) -> CIImage {
+    func blendLayer(document: SilicaDocument, layer : SilicaLayer, previousImage : inout CGImage?) -> CIImage? {
         let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue).union(.byteOrder32Big)
         
         // start by creating a new layer composite image, needed for image masking
@@ -187,21 +197,25 @@ class SilicaEngine {
         
         layerContext?.clear(document.cgRect())
         
-        let kernel = getBlendKernel(layer)
+        guard let kernel = getBlendKernel(layer) else {
+            return nil
+        }
         
         for chunk in layer.data.chunks {
             layerContext?.setAlpha(CGFloat(layer.data.opacity))
             layerContext?.setBlendMode(.normal)
             
             if !layer.data.hidden {
-                layerContext?.draw(chunk.image!, in: document.getChunkRect(chunk))
+                if let image = chunk.image {
+                    layerContext?.draw(image, in: document.getChunkRect(chunk))
+                }
             }
         }
         
         let layerImage = layerContext?.makeImage()
         
         // apply image
-        return kernel!.apply(foreground: CIImage(cgImage: layerImage!), background: previousImage == nil ? CIImage(color: .clear) : CIImage(cgImage: previousImage!), colorSpace: document.colorSpace)!
+        return kernel.apply(foreground: CIImage(cgImage: layerImage!), background: previousImage == nil ? CIImage(color: .clear) : CIImage(cgImage: previousImage!), colorSpace: document.colorSpace)!
     }
     
     /// Figures out the correct `CIBlendKernel` corresponding to the `SilicaLayer`'s blending mode.