Fix some warnings raised by MSVC 2017

Disabled signed/unsigned warnings like for GCC/Clang
(warning C4018: '>=': signed/unsigned mismatch).

Fixes the following MSVC 2017 warnings:
```
core\image.cpp(999): warning C4804: '>': unsafe use of type 'bool' in operation

core\io\compression.cpp(178): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
editor\doc\doc_dump.cpp(226): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
scene/resources/material.h(289): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)
scene/resources/material.h(298): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)

editor\editor_themes.cpp(379): warning C4805: '==': unsafe mix of type 'int' and type 'bool' in operation
```

SConstruct

@@ -322,13 +322,13 @@ if selected_platform in platform_list:
         print("WARNING: warnings=yes is deprecated; assuming warnings=all")
 
     if env.msvc:
-        disable_nonessential_warnings = ['/wd4267', '/wd4244', '/wd4305', '/wd4800'] # Truncations, narrowing conversions...
+        # Truncations, narrowing conversions, signed/unsigned comparisons...
+        disable_nonessential_warnings = ['/wd4267', '/wd4244', '/wd4305', '/wd4018', '/wd4800']
         if (env["warnings"] == 'extra'):
             env.Append(CCFLAGS=['/Wall']) # Implies /W4
         elif (env["warnings"] == 'all' or env["warnings"] == 'yes'):
             env.Append(CCFLAGS=['/W3'] + disable_nonessential_warnings)
         elif (env["warnings"] == 'moderate'):
-            # C4244 shouldn't be needed here being a level-3 warning, but it is
             env.Append(CCFLAGS=['/W2'] + disable_nonessential_warnings)
         else: # 'no'
             env.Append(CCFLAGS=['/w'])

core/image.cpp

@@ -307,6 +307,7 @@ void Image::_get_mipmap_offset_and_size(int p_mipmap, int &r_offset, int &r_widt
 	r_width = w;
 	r_height = h;
 }
+
 int Image::get_mipmap_offset(int p_mipmap) const {
 
 	ERR_FAIL_INDEX_V(p_mipmap, get_mipmap_count() + 1, -1);
@@ -499,8 +500,6 @@ void Image::convert(Format p_new_format) {
 
 	bool gen_mipmaps = mipmaps;
 
-	//mipmaps=false;
-
 	_copy_internals_from(new_img);
 
 	if (gen_mipmaps)
@@ -799,6 +798,7 @@ void Image::resize(int p_width, int p_height, Interpolation p_interpolation) {
 	if (interpolate_mipmaps) {
 		dst2.create(p_width, p_height, 0, format);
 	}
+
 	bool had_mipmaps = mipmaps;
 	if (interpolate_mipmaps && !had_mipmaps) {
 		generate_mipmaps();
@@ -951,6 +951,7 @@ void Image::resize(int p_width, int p_height, Interpolation p_interpolation) {
 }
 
 void Image::crop_from_point(int p_x, int p_y, int p_width, int p_height) {
+
 	if (!_can_modify(format)) {
 		ERR_EXPLAIN("Cannot crop in indexed, compressed or custom image formats.");
 		ERR_FAIL();
@@ -996,7 +997,7 @@ void Image::crop_from_point(int p_x, int p_y, int p_width, int p_height) {
 		}
 	}
 
-	if (mipmaps > 0)
+	if (has_mipmaps())
 		dst.generate_mipmaps();
 	_copy_internals_from(dst);
 }
@@ -1013,10 +1014,10 @@ void Image::flip_y() {
 		ERR_FAIL();
 	}
 
-	bool gm = mipmaps;
-
-	if (gm)
+	bool used_mipmaps = has_mipmaps();
+	if (used_mipmaps) {
 		clear_mipmaps();
+	}
 
 	{
 		PoolVector<uint8_t>::Write w = data.write();
@@ -1037,9 +1038,10 @@ void Image::flip_y() {
 		}
 	}
 
-	if (gm)
+	if (used_mipmaps) {
 		generate_mipmaps();
 	}
+}
 
 void Image::flip_x() {
 
@@ -1048,9 +1050,10 @@ void Image::flip_x() {
 		ERR_FAIL();
 	}
 
-	bool gm = mipmaps;
-	if (gm)
+	bool used_mipmaps = has_mipmaps();
+	if (used_mipmaps) {
 		clear_mipmaps();
+	}
 
 	{
 		PoolVector<uint8_t>::Write w = data.write();
@@ -1071,9 +1074,10 @@ void Image::flip_x() {
 		}
 	}
 
-	if (gm)
+	if (used_mipmaps) {
 		generate_mipmaps();
 	}
+}
 
 int Image::_get_dst_image_size(int p_width, int p_height, Format p_format, int &r_mipmaps, int p_mipmaps) {
 
@@ -1167,12 +1171,13 @@ void Image::expand_x2_hq2x() {
 
 	ERR_FAIL_COND(!_can_modify(format));
 
-	Format current = format;
-	bool mm = has_mipmaps();
-	if (mm) {
+	bool used_mipmaps = has_mipmaps();
+	if (used_mipmaps) {
 		clear_mipmaps();
 	}
 
+	Format current = format;
+
 	if (current != FORMAT_RGBA8)
 		convert(FORMAT_RGBA8);
 
@@ -1193,7 +1198,7 @@ void Image::expand_x2_hq2x() {
 	if (current != FORMAT_RGBA8)
 		convert(current);
 
-	if (mipmaps) {
+	if (used_mipmaps) {
 		generate_mipmaps();
 	}
 }

core/io/compression.cpp

@@ -175,7 +175,7 @@ int Compression::decompress(uint8_t *p_dst, int p_dst_max_size, const uint8_t *p
 		} break;
 		case MODE_ZSTD: {
 			ZSTD_DCtx *dctx = ZSTD_createDCtx();
-			if (zstd_long_distance_matching) ZSTD_DCtx_setMaxWindowSize(dctx, 1 << zstd_window_log_size);
+			if (zstd_long_distance_matching) ZSTD_DCtx_setMaxWindowSize(dctx, (size_t)1 << zstd_window_log_size);
 			int ret = ZSTD_decompressDCtx(dctx, p_dst, p_dst_max_size, p_src, p_src_size);
 			ZSTD_freeDCtx(dctx);
 			return ret;

editor/doc/doc_dump.cpp

@@ -223,7 +223,7 @@ void DocDump::dump(const String &p_file) {
 						hint = "Values: ";
 						for (int j = 0; j < arginfo.hint_string.get_slice_count(","); j++) {
 							if (j > 0) hint += ", ";
-							hint += arginfo.hint_string.get_slice(",", j) + "=" + itos(1 << j);
+							hint += arginfo.hint_string.get_slice(",", j) + "=" + itos((uint64_t)1 << j);
 						}
 						break;
 					case PROPERTY_HINT_FILE: hint = "A file:"; break;

editor/editor_themes.cpp

@@ -376,7 +376,7 @@ Ref<Theme> create_editor_theme(const Ref<Theme> p_theme) {
 	//Register icons + font
 
 	// the resolution and the icon color (dark_theme bool) has not changed, so we do not regenerate the icons
-	if (p_theme != NULL && fabs(p_theme->get_constant("scale", "Editor") - EDSCALE) < 0.00001 && p_theme->get_constant("dark_theme", "Editor") == dark_theme) {
+	if (p_theme != NULL && fabs(p_theme->get_constant("scale", "Editor") - EDSCALE) < 0.00001 && (bool)p_theme->get_constant("dark_theme", "Editor") == dark_theme) {
 		// register already generated icons
 		for (int i = 0; i < editor_icons_count; i++) {
 			theme->set_icon(editor_icons_names[i], "EditorIcons", p_theme->get_icon(editor_icons_names[i], "EditorIcons"));

scene/resources/material.h

@@ -286,7 +286,7 @@ private:
 		mk.key = 0;
 		for (int i = 0; i < FEATURE_MAX; i++) {
 			if (features[i]) {
-				mk.feature_mask |= (1 << i);
+				mk.feature_mask |= ((uint64_t)1 << i);
 			}
 		}
 		mk.detail_uv = detail_uv;
@@ -295,7 +295,7 @@ private:
 		mk.cull_mode = cull_mode;
 		for (int i = 0; i < FLAG_MAX; i++) {
 			if (flags[i]) {
-				mk.flags |= (1 << i);
+				mk.flags |= ((uint64_t)1 << i);
 			}
 		}
 		mk.detail_blend_mode = detail_blend_mode;